Business Combinations - Net Assets Acquired (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	Mar. 20, 2023	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Fair value adjustments:
Bargain purchase gain on Signature Transaction, as initially reported		$ 0	$ 0	$ 2,142	$ 0
Restatement Adjustment
Fair value adjustments:
Measurement period adjustments, excluding taxes	$ 53
Change in deferred tax liability	88
Signature Bridge Bank
Business Acquisition [Line Items]
Net assets acquired before fair value adjustments	2,973
Fair value adjustments:
Loans	(727)
Core deposit and other intangibles	464
Certificates of deposit	27
Other net assets and liabilities	39
FDIC Equity Appreciation Instrument	(85)
Deferred tax liability	(690)
Bargain purchase gain on Signature Transaction, as initially reported	2,142			$ 2,100
Signature Bridge Bank | Previously Reported
Fair value adjustments:
Bargain purchase gain on Signature Transaction, as initially reported	$ 2,001