Business Combinations - Narrative (Details) $ in Millions			3 Months Ended		9 Months Ended
	Mar. 31, 2023 shares	Mar. 20, 2023 USD ($) branch	Sep. 30, 2023 USD ($) branch	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) branch	Sep. 30, 2022 USD ($)
Business Acquisition [Line Items]
Number of branches			436		436
Bargain purchase gain | $			$ 0	$ 0	$ 2,142	$ 0
Loans returned to the FDIC | $					449
Signature Bridge Bank
Business Acquisition [Line Items]
Bargain purchase gain | $		$ 2,142			$ 2,100
Signature Bridge Bank | Core Deposits
Business Acquisition [Line Items]
Estimated useful life		10 years
Signature Bridge Bank | FDIC
Business Acquisition [Line Items]
Shares issued (in shares) | shares	39,032,006
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