Regulatory Capital - U.S. Basel III Regulatory Requirements (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Actual Amount
Common Equity Tier 1 Capital (to Risk-Weighted Assets)	$ 2,977,353	$ 3,019,973
Tier 1 Capital (to Risk-Weighted Assets)	2,977,353	3,019,973
Total Capital (to Risk-Weighted Assets)	3,290,809	3,334,140
Tier 1 Capital (to Average Assets)	$ 2,977,353	$ 3,019,973
Actual Ratio
Common Equity Tier 1 Capital (to Risk-Weighted Assets)	12.30%	12.30%
Tier 1 Capital (to Risk-Weighted Assets)	0.123	0.123
Total Capital (to Risk-Weighted Assets)	0.135	0.136
Tier 1 Capital (to Average Assets)	0.102	0.102
U.S. Basel III Regulatory Requirements, Amount
Common Equity Tier 1 Capital (to Risk-Weighted Assets)	$ 1,700,543	$ 1,719,621
Tier 1 Capital (to Risk-Weighted Assets)	2,064,945	2,088,111
Total Capital (to Risk-Weighted Assets)	2,550,814	2,579,432
Tier 1 Capital (to Average Assets)	$ 1,170,715	$ 1,184,213
U.S. Basel III Regulatory Requirements, Ratio
Common Equity Tier 1 Capital (to Risk-Weighted Assets)	7.00%	7.00%
Tier 1 Capital (to Risk-Weighted Assets)	0.085	0.085
Total Capital (to Risk-Weighted Assets)	0.105	0.105
Tier 1 Capital (to Average Assets)	0.040	0.040