Employee benefit plans - Fair Value Measurements of Pension Plans' Assets (Details) - Pension plans - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plans' assets	$ 141,423	$ 126,419	$ 136,653	$ 137,294
Actual allocation	100.00%	100.00%
Level 1
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plans' assets	$ 2,265	$ 1,563
Level 2
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plans' assets	128,226	114,635
Level 3
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plans' assets	10,932	10,221
US government and federal agencies
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plans' assets	31,191	30,748
US government and federal agencies \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plans' assets	0	0
US government and federal agencies \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plans' assets	31,191	30,748
US government and federal agencies \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plans' assets	0	0
Non-US governments debt securities
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plans' assets	41,404	39,127
Non-US governments debt securities \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plans' assets	0	0
Non-US governments debt securities \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plans' assets	41,404	39,127
Non-US governments debt securities \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plans' assets	0	0
Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plans' assets	28,475	19,137
Corporate debt securities \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plans' assets	0	0
Corporate debt securities \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plans' assets	28,475	19,137
Corporate debt securities \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plans' assets	0	0
Equity securities (including equity mutual funds)
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plans' assets	$ 27,313	$ 25,856
Actual allocation	19.00%	20.00%
Equity securities (including equity mutual funds) \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plans' assets	$ 1,491	$ 1,066
Equity securities (including equity mutual funds) \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plans' assets	25,822	24,790
Equity securities (including equity mutual funds) \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plans' assets	0	0
Other
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plans' assets	$ 13,040	$ 11,551
Actual allocation	9.00%	10.00%
Other \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plans' assets	$ 774	$ 497
Other \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plans' assets	1,334	833
Other \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plans' assets	$ 10,932	$ 10,221
Mutual Funds and Equity Securities Managed or Administered by Wholly-Owned Subsidiaries
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	19.00%	19.50%
Parent Company Common Stock \| Voting Common Stock
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	1.10%	0.80%