v3.25.4
Credit risk concentrations (Details) - Credit Availability Concentration Risk - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Total credit exposure    
Concentration Risk [Line Items]    
Total gross exposure $ 8,794,249 $ 8,997,688
Total credit exposure | Belgium    
Concentration Risk [Line Items]    
Total gross exposure 3,568 2,478
Total credit exposure | Bermuda    
Concentration Risk [Line Items]    
Total gross exposure 1,831,063 1,854,898
Total credit exposure | Canada    
Concentration Risk [Line Items]    
Total gross exposure 1,276,109 1,417,882
Total credit exposure | Cayman Islands    
Concentration Risk [Line Items]    
Total gross exposure 1,265,414 1,327,634
Total credit exposure | France    
Concentration Risk [Line Items]    
Total gross exposure 117,550 207,687
Total credit exposure | Germany    
Concentration Risk [Line Items]    
Total gross exposure 6,121 1,178
Total credit exposure | Guernsey    
Concentration Risk [Line Items]    
Total gross exposure 640,864 656,974
Total credit exposure | Ireland    
Concentration Risk [Line Items]    
Total gross exposure 26,027 8,672
Total credit exposure | Japan    
Concentration Risk [Line Items]    
Total gross exposure 102,407 121,862
Total credit exposure | Jersey    
Concentration Risk [Line Items]    
Total gross exposure 371,856 292,181
Total credit exposure | Mauritius    
Concentration Risk [Line Items]    
Total gross exposure 686 1,055
Total credit exposure | Norway    
Concentration Risk [Line Items]    
Total gross exposure 90,585 100,148
Total credit exposure | Switzerland    
Concentration Risk [Line Items]    
Total gross exposure 9,642 3,377
Total credit exposure | The Bahamas    
Concentration Risk [Line Items]    
Total gross exposure 3,081 3,975
Total credit exposure | United Kingdom    
Concentration Risk [Line Items]    
Total gross exposure 2,557,065 2,396,718
Total credit exposure | United States    
Concentration Risk [Line Items]    
Total gross exposure 490,782 599,264
Total credit exposure | Other    
Concentration Risk [Line Items]    
Total gross exposure 1,429 1,705
Cash and cash equivalents, resell agreements and short-term investments    
Concentration Risk [Line Items]    
Total gross exposure 3,561,717 3,783,511
Cash and cash equivalents, resell agreements and short-term investments | Belgium    
Concentration Risk [Line Items]    
Total gross exposure 3,568 2,478
Cash and cash equivalents, resell agreements and short-term investments | Bermuda    
Concentration Risk [Line Items]    
Total gross exposure 41,849 37,227
Cash and cash equivalents, resell agreements and short-term investments | Canada    
Concentration Risk [Line Items]    
Total gross exposure 1,276,109 1,417,882
Cash and cash equivalents, resell agreements and short-term investments | Cayman Islands    
Concentration Risk [Line Items]    
Total gross exposure 37,633 40,675
Cash and cash equivalents, resell agreements and short-term investments | France    
Concentration Risk [Line Items]    
Total gross exposure 117,550 207,687
Cash and cash equivalents, resell agreements and short-term investments | Germany    
Concentration Risk [Line Items]    
Total gross exposure 6,121 1,178
Cash and cash equivalents, resell agreements and short-term investments | Guernsey    
Concentration Risk [Line Items]    
Total gross exposure 1 1
Cash and cash equivalents, resell agreements and short-term investments | Ireland    
Concentration Risk [Line Items]    
Total gross exposure 26,027 8,672
Cash and cash equivalents, resell agreements and short-term investments | Japan    
Concentration Risk [Line Items]    
Total gross exposure 102,407 121,862
Cash and cash equivalents, resell agreements and short-term investments | Jersey    
Concentration Risk [Line Items]    
Total gross exposure 0 0
Cash and cash equivalents, resell agreements and short-term investments | Mauritius    
Concentration Risk [Line Items]    
Total gross exposure 686 1,055
Cash and cash equivalents, resell agreements and short-term investments | Norway    
Concentration Risk [Line Items]    
Total gross exposure 90,585 100,148
Cash and cash equivalents, resell agreements and short-term investments | Switzerland    
Concentration Risk [Line Items]    
Total gross exposure 9,642 3,377
Cash and cash equivalents, resell agreements and short-term investments | The Bahamas    
Concentration Risk [Line Items]    
Total gross exposure 186 184
Cash and cash equivalents, resell agreements and short-term investments | United Kingdom    
Concentration Risk [Line Items]    
Total gross exposure 1,357,142 1,240,116
Cash and cash equivalents, resell agreements and short-term investments | United States    
Concentration Risk [Line Items]    
Total gross exposure 490,782 599,264
Cash and cash equivalents, resell agreements and short-term investments | Other    
Concentration Risk [Line Items]    
Total gross exposure 1,429 1,705
Loans    
Concentration Risk [Line Items]    
Total gross exposure 4,407,787 4,499,300
Loans | Belgium    
Concentration Risk [Line Items]    
Total gross exposure 0 0
Loans | Bermuda    
Concentration Risk [Line Items]    
Total gross exposure 1,471,971 1,631,461
Loans | Canada    
Concentration Risk [Line Items]    
Total gross exposure 0 0
Loans | Cayman Islands    
Concentration Risk [Line Items]    
Total gross exposure 1,029,012 1,068,142
Loans | France    
Concentration Risk [Line Items]    
Total gross exposure 0 0
Loans | Germany    
Concentration Risk [Line Items]    
Total gross exposure 0 0
Loans | Guernsey    
Concentration Risk [Line Items]    
Total gross exposure 541,110 552,994
Loans | Ireland    
Concentration Risk [Line Items]    
Total gross exposure 0 0
Loans | Japan    
Concentration Risk [Line Items]    
Total gross exposure 0 0
Loans | Jersey    
Concentration Risk [Line Items]    
Total gross exposure 306,190 223,964
Loans | Mauritius    
Concentration Risk [Line Items]    
Total gross exposure 0 0
Loans | Norway    
Concentration Risk [Line Items]    
Total gross exposure 0 0
Loans | Switzerland    
Concentration Risk [Line Items]    
Total gross exposure 0 0
Loans | The Bahamas    
Concentration Risk [Line Items]    
Total gross exposure 2,895 3,791
Loans | United Kingdom    
Concentration Risk [Line Items]    
Total gross exposure 1,056,609 1,018,948
Loans | United States    
Concentration Risk [Line Items]    
Total gross exposure 0 0
Loans | Other    
Concentration Risk [Line Items]    
Total gross exposure 0 0
Off-balance sheet    
Concentration Risk [Line Items]    
Total gross exposure 824,745 714,877
Off-balance sheet | Belgium    
Concentration Risk [Line Items]    
Total gross exposure 0 0
Off-balance sheet | Bermuda    
Concentration Risk [Line Items]    
Total gross exposure 317,243 186,210
Off-balance sheet | Canada    
Concentration Risk [Line Items]    
Total gross exposure 0 0
Off-balance sheet | Cayman Islands    
Concentration Risk [Line Items]    
Total gross exposure 198,769 218,817
Off-balance sheet | France    
Concentration Risk [Line Items]    
Total gross exposure 0 0
Off-balance sheet | Germany    
Concentration Risk [Line Items]    
Total gross exposure 0 0
Off-balance sheet | Guernsey    
Concentration Risk [Line Items]    
Total gross exposure 99,753 103,979
Off-balance sheet | Ireland    
Concentration Risk [Line Items]    
Total gross exposure 0 0
Off-balance sheet | Japan    
Concentration Risk [Line Items]    
Total gross exposure 0 0
Off-balance sheet | Jersey    
Concentration Risk [Line Items]    
Total gross exposure 65,666 68,217
Off-balance sheet | Mauritius    
Concentration Risk [Line Items]    
Total gross exposure 0 0
Off-balance sheet | Norway    
Concentration Risk [Line Items]    
Total gross exposure 0 0
Off-balance sheet | Switzerland    
Concentration Risk [Line Items]    
Total gross exposure 0 0
Off-balance sheet | The Bahamas    
Concentration Risk [Line Items]    
Total gross exposure 0 0
Off-balance sheet | United Kingdom    
Concentration Risk [Line Items]    
Total gross exposure 143,314 137,654
Off-balance sheet | United States    
Concentration Risk [Line Items]    
Total gross exposure 0 0
Off-balance sheet | Other    
Concentration Risk [Line Items]    
Total gross exposure $ 0 $ 0