Minimum Regulatory Capital Requirements (Details) $ in Thousands	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Total regulatory capital (to risk-weighted assets)
Actual, Amount	$ 2,939,016	$ 3,135,445
Actual, Ratio	19.77	29.61
For Capital Adequacy, Amount	$ 1,189,466	$ 847,069
For Capital Adequacy, Ratio (less than)	0.08	0.08
To Be Well-Capitalized Under Prompt Corrective Action Provisions, Amount	$ 1,486,832	$ 1,058,836
To Be Well-Capitalized Under Prompt Corrective Action Provisions, Ratio (less than)	0.10	0.10
Common equity Tier 1 capital (to risk-weighted assets)
Actual, Amount	$ 2,831,102	$ 3,013,079
Actual, Ratio	19.04	28.46
For Capital Adequacy, Amount	$ 892,099	$ 476,476
For Capital Adequacy, Ratio	4.5	4.5
To Be Well-Capitalized Under Prompt Corrective Action Provisions, Amount	$ 1,189,466	$ 688,243
To Be Well-Capitalized Under Prompt Corrective Action Provisions, Ratio	6.5	6.5
Tier 1 capital (to risk-weighted assets)
Actual, Amount	$ 2,831,102	$ 3,013,079
Actual, Ratio	19.04	28.46
For Capital Adequacy, Amount	$ 669,075	$ 635,302
For Capital Adequacy, Ratio	6	6
To Be Well-Capitalized Under Prompt Corrective Action Provisions, Amount	$ 966,441	$ 847,069
To Be Well-Capitalized Under Prompt Corrective Action Provisions, Ratio	8	8
Tier I capital (to average assets)
Actual, Amount	$ 2,831,102	$ 3,013,079
Actual, Ratio	13.96	19.53
For Capital Adequacy, Amount	$ 811,000	$ 617,049
For Capital Adequacy, Ratio	4	4
To Be Well-Capitalized Under Prompt Corrective Action Provisions, Amount	$ 1,013,750	$ 771,312
To Be Well-Capitalized Under Prompt Corrective Action Provisions, Ratio	5	5