Loans and Leases - Composition of Loan and Lease Portfolio (Details) - USD ($) $ in Millions		Mar. 31, 2022		Dec. 31, 2021		Mar. 31, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	[1]	$ 46,703		$ 45,681
Non-Covered Loans, Percentage	[1]	100.00%		100.00%
Net deferred loan origination costs		$ 55		$ 57
Allowance for loan and lease losses		(197)		(199)		$ (198)	$ (194)
Total loans and leases, net		46,561		45,539
Multi-Family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 35,751		$ 34,603
Non-Covered Loans, Percentage		76.55%		75.75%
Commercial Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 6,701		$ 6,698
Non-Covered Loans, Percentage		14.35%		14.66%
One-to-Four Family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 145		$ 160
Non-Covered Loans, Percentage		0.31%		0.35%
Acquisition, Development, and Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 237		$ 209
Non-Covered Loans, Percentage		0.51%		0.46%
Mortgage Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	[1]	$ 42,834		$ 41,670
Non-Covered Loans, Percentage	[1]	91.72%		91.22%
Allowance for loan and lease losses		$ (176)		$ (178)		$ (176)	$ (176)
Commercial and Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans	[3]	$ 3,863	[2]	$ 4,006	[4]
Non-Covered Loans, Percentage	[3]	8.27%		8.77%
Commercial and Industrial | Other Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 2,200		$ 2,236
Non-Covered Loans, Percentage		4.71%		4.89%
Lease Financing, Unearned Income
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 1,663		$ 1,770
Non-Covered Loans, Percentage		3.57%		3.88%
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 6		$ 5
Non-Covered Loans, Percentage		0.01%		0.01%
Total Other Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 3,869		$ 4,011
Total Other Loans | Other Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-Covered Loans		$ 3,869		$ 4,011
Non-Covered Loans, Percentage		8.28%		8.78%

[1] Excludes accrued interest receivable of $200 million and $199 million at March 31, 2022 and December 31, 2021, respectively, which is included in other assets in the Consolidated Statements of Condition.

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

[3] Includes specialty finance loans and leases of $3.3 billion and $3.5 billion, respectively, at March 31, 2022 and December 31, 2021, and other C&I loans of $548 million and $527 million, respectively, at March 31, 2022 and December 31, 2021.

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