Regulatory Capital - U.S. Basel III Regulatory Requirements (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Actual Amount
Common Equity Tier 1 Capital (to Risk-Weighted Assets)	$ 3,019,973	$ 3,040,662
Tier 1 Capital (to Risk-Weighted Assets)	3,019,973	3,040,662
Total Capital (to Risk-Weighted Assets)	3,334,140	3,338,645
Tier 1 Capital (to Average Assets)	$ 3,019,973	$ 3,040,662
Actual Ratio
Common Equity Tier 1 Capital (to Risk-Weighted Assets)	12.30%	12.90%
Tier 1 Capital (to Risk-Weighted Assets)	0.123	0.129
Total Capital (to Risk-Weighted Assets)	0.136	0.142
Tier 1 Capital (to Average Assets)	0.102	0.103
Well Capitalized Regulatory Requirements, Amount
Common Equity Tier 1 Capital (to Risk-Weighted Assets)	$ 1,719,621	$ 1,645,807
Tier 1 Capital (to Risk-Weighted Assets)	2,088,111	1,998,480
Total Capital (to Risk-Weighted Assets)	2,579,432	2,468,711
Tier 1 Capital (to Average Assets)	$ 1,184,213	$ 1,185,280
Well Capitalized 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