v3.24.1.1.u2
Debt - Senior Unsecured Notes (Details) - USD ($)
$ in Millions
1 Months Ended
Sep. 18, 2023
Jun. 22, 2023
May 04, 2021
Apr. 12, 2021
Apr. 30, 2021
May 04, 2024
Feb. 03, 2024
Jun. 22, 2018
Debt Instrument [Line Items]                
Long-term debt           $ 4,145.9 $ 4,165.9  
Notes                
Debt Instrument [Line Items]                
Redemption price percentage       101.00%        
Long-term debt           $ 2,000.0    
5.750% 2029 Senior Notes | Notes                
Debt Instrument [Line Items]                
Aggregate principal amount $ 500.0              
Stated interest rate 5.75%         5.75%    
Debt term (in years) 5 years 6 months              
Effective interest rate 5.891%              
5.950% 2033 Senior Notes | Notes                
Debt Instrument [Line Items]                
Aggregate principal amount $ 500.0              
Stated interest rate 5.95%         5.95%    
Debt term (in years) 10 years              
Effective interest rate 6.082%              
Senior Notes Due 2029 and 2033 | Notes                
Debt Instrument [Line Items]                
Redemption price percentage 101.00%              
Long-term debt           $ 1,000.0    
Senior Notes Due 2026 | Notes                
Debt Instrument [Line Items]                
Aggregate principal amount       $ 500.0        
Stated interest rate       1.65%   1.65%    
Debt term (in years)       5 years        
Effective interest rate       1.839%        
Senior Notes Due 2028 | Notes                
Debt Instrument [Line Items]                
Aggregate principal amount       $ 750.0        
Stated interest rate       2.45%   2.45%    
Debt term (in years)       7 years        
Effective interest rate       2.554%        
Senior Notes Due 2031 | Notes                
Debt Instrument [Line Items]                
Aggregate principal amount       $ 750.0        
Stated interest rate       2.95%   2.95%    
Debt term (in years)       10 years        
Effective interest rate       3.043%        
MTG Senior Notes Due 2023 | Notes                
Debt Instrument [Line Items]                
Aggregate principal amount               $ 500.0
Stated interest rate               4.20%
Principal amount exchanged     $ 433.9          
MTG Senior Notes Due 2028 | Notes                
Debt Instrument [Line Items]                
Aggregate principal amount         $ 500.0     $ 500.0
Stated interest rate         4.875%     4.875%
Effective interest rate         4.94%      
Principal amount exchanged     $ 479.5          
MTG Senior Notes | Notes                
Debt Instrument [Line Items]                
Long-term debt         $ 1,000.0      
MTI Senior Notes Due 2023 | Notes                
Debt Instrument [Line Items]                
Aggregate principal amount         $ 500.0      
Stated interest rate         4.20%      
MTI and MTG 2023 Notes | Notes                
Debt Instrument [Line Items]                
Repayments of senior notes   $ 500.0            
MTI Senior Notes Due 2028 | Notes                
Debt Instrument [Line Items]                
Stated interest rate         4.875%      
Effective interest rate         4.988%      
MTI Senior Notes | Notes                
Debt Instrument [Line Items]                
Redemption price percentage         101.00%      
MTG and MTI 2028 Senior Notes | Notes                
Debt Instrument [Line Items]                
Long-term debt           $ 499.9