Business Combinations - Narrative (Details) $ in Millions				12 Months Ended
	Mar. 31, 2023 shares	Mar. 20, 2023 USD ($) branch	Dec. 01, 2022 USD ($) loan States shares	Dec. 31, 2023 USD ($) branch	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Business Acquisition [Line Items]
Number of branches				420
Bargain purchase gain | $			$ 159	$ 2,131	$ 159	$ 0
Loans returned to the FDIC | $				$ 449
Core Deposits
Business Acquisition [Line Items]
Estimated useful life				10 years
Signature Bridge Bank
Business Acquisition [Line Items]
Shares issued (in shares) | shares	39,032,006
Acquisition costs | $		$ 223
Signature Bridge Bank | Core Deposits
Business Acquisition [Line Items]
Estimated useful life		10 years
Signature Bridge Bank | New York
Business Acquisition [Line Items]
Number of branches		29
Signature Bridge Bank | California
Business Acquisition [Line Items]
Number of branches		7
Signature Bridge Bank | North Carolina
Business Acquisition [Line Items]
Number of branches		2
Signature Bridge Bank | Connecticut
Business Acquisition [Line Items]
Number of branches		1
Signature Bridge Bank | Nevada
Business Acquisition [Line Items]
Number of branches		1
Flagstar Bancorp
Business Acquisition [Line Items]
Shares issued (in shares) | shares			4.0151
Bargain purchase gain | $			$ 159
Acquisition costs | $			$ 99
Number of states in which offices are located | States			50
Flagstar Bancorp | INDIANA
Business Acquisition [Line Items]
Number of branches | loan			158