Regulatory Capital - U.S. Basel III Regulatory Requirements (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Actual Amount
Common Equity Tier 1 Capital (to Risk-Weighted Assets)	$ 2,935,903	$ 3,040,662
Tier 1 Capital (to Risk-Weighted Assets)	2,935,903	3,040,662
Total Capital (to Risk-Weighted Assets)	3,258,771	3,338,645
Tier 1 Capital (to Average Assets)	$ 2,935,903	$ 3,040,662
Actual Ratio
Common Equity Tier 1 Capital (to Risk-Weighted Assets)	11.70%	12.90%
Tier 1 Capital (to Risk-Weighted Assets)	0.117	0.129
Total Capital (to Risk-Weighted Assets)	0.129	0.142
Tier 1 Capital (to Average Assets)	0.101	0.103
U.S. Basel III Regulatory Requirements, Amount
Common Equity Tier 1 Capital (to Risk-Weighted Assets)	$ 1,763,562	$ 1,645,807
Tier 1 Capital (to Risk-Weighted Assets)	2,141,468	1,998,480
Total Capital (to Risk-Weighted Assets)	2,645,343	2,468,711
Tier 1 Capital (to Average Assets)	$ 1,166,116	$ 1,185,280
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