Loans and Leases - Additional Information (Details)		12 Months Ended
		Dec. 31, 2022 USD ($) Investment		Dec. 31, 2021 USD ($) Investment		Dec. 31, 2020 USD ($)
Financing Receivable, Recorded Investment [Line Items]
Outstanding loans to Executive officers, directors, principal shareholders, related interest and parties		$ 101,000,000		$ 6,000,000
Debt instrument, term		10 years
Loans with government guarantees		$ 1,200,000,000
Repurchase liability		300,000,000
Repossessed assets and associated claims		8,000,000		3,000,000
Total loans receivable	[1]	69,001,000,000		45,738,000,000
Net gain on loan sales		5,000,000
Flagstar
Financing Receivable, Recorded Investment [Line Items]
Loans held-for-sale		1,100,000,000		0
Other Assets
Financing Receivable, Recorded Investment [Line Items]
Repossessed assets and associated claims		14,000,000
Commercial and Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans receivable	[3]	$ 12,276,000,000	[2]	$ 4,034,000,000	[4]
Loan classified as non accrual TDRs						$ 3,000,000
Number of financing receivable contracts modified as TDRs within previous 12 months, with payment default | Investment		0		0
One-to-Four Family First Mortgage
Financing Receivable, Recorded Investment [Line Items]
Total loans receivable		$ 5,821,000,000		$ 160,000,000
One-to-Four Family First Mortgage | Flagstar
Financing Receivable, Recorded Investment [Line Items]
Total loans receivable		5,800,000,000		160,000,000
One-to-Four Family
Financing Receivable, Recorded Investment [Line Items]
Total loans receivable		5,821,000,000		160,000,000
Other
Financing Receivable, Recorded Investment [Line Items]
Total loans receivable		2,252,000,000		6,000,000
Other | Flagstar
Financing Receivable, Recorded Investment [Line Items]
Total loans receivable		2,300,000,000
Residential Mortgage
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable, loans in process of foreclosure		121,000,000		0
Financing Receivable Troubled Debt Restructurings Rate Reductions
Financing Receivable, Recorded Investment [Line Items]
Loans and leases receivable, loans in process of foreclosure		38,000,000
Other Loans | Commercial and Industrial
Financing Receivable, Recorded Investment [Line Items]
Total loans receivable		$ 10,597,000,000		$ 2,238,000,000

[1] Excludes accrued interest receivable of $292 million and $199 million at December 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 $4.4 billion and $3.5 billion, respectively, at December 31, 2022 and December 31, 2021.

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