Loans and Leases - Composition of Loan and Lease Portfolio (Details) - USD ($) $ in Millions		Dec. 31, 2021		Dec. 31, 2020		Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	[1]	$ 45,681		$ 42,822
Non-Covered Loans, Percentage	[1]	100.00%		100.00%
Net deferred loan origination costs		$ 57		$ 62
Allowance for loan and lease losses		(199)		(194)		$ (148)
Total loans and leases held for investment, net		45,539		42,690
Loans held for sale	[2]			117
Total loans and leases, net		45,539		42,807
Multi-Family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 34,603		$ 32,236
Non-Covered Loans, Percentage		75.75%		75.28%
Commercial Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 6,698		$ 6,836
Non-Covered Loans, Percentage		14.66%		15.96%
One-to-Four Family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 160		$ 236
Non-Covered Loans, Percentage		0.35%		0.55%
Acquisition, Development, and Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 209		$ 90
Non-Covered Loans, Percentage		0.46%		0.21%
Mortgage Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 41,670		$ 39,398
Non-Covered Loans, Percentage		91.22%		92.00%
Allowance for loan and lease losses		$ (178)		$ (176)		$ (123)
Commercial and Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	[4]	$ 4,006	[3]	$ 3,417	[5]
Non-Covered Loans, Percentage	[4]	8.77%		7.98%
Commercial and Industrial | Other Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 2,236		$ 1,682
Non-Covered Loans, Percentage		4.89%		3.93%
Lease Financing, Unearned Income
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 1,770		$ 1,735
Non-Covered Loans, Percentage		3.88%		4.05%
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 5		$ 7
Non-Covered Loans, Percentage		0.01%		0.02%
Total Other Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 4,011		$ 3,424
Total Other Loans | Other Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 4,011		$ 3,424
Non-Covered Loans, Percentage		8.78%		8.00%

[1] Excludes accrued interest receivable of $199 million and $219 million at December 31, 2021 and December 31, 2020, respectively, which is included in other assets in the Consolidated Statements of Condition.

[2] Includes deferred loan origination fees of $2 million.

[3] Includes lease financing receivables, all of which were classified as Pass.

[4] Includes specialty finance loans and leases of $3.5 billion and $3.0 billion, respectively, at December 31, 2021 and December 31, 2020, and other C&I loans of $527 million and $393 million, respectively, at December 31, 2021 and December 31, 2020.

[5] Includes lease financing receivables, all of which were classified as Pass.