Investment Securities - Investment Securities, Narrative (Details)	3 Months Ended			9 Months Ended
	Sep. 30, 2023 USD ($) loan	Mar. 31, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) loan	Sep. 30, 2022 USD ($)	Mar. 12, 2023 USD ($)	Dec. 31, 2022 USD ($) loan
Schedule of Investments [Line Items]
Federal home loan bank stock | $	$ 1,110,000,000			$ 1,110,000,000			$ 1,267,000,000
Federal reserve bank stock | $	203,000,000			203,000,000			176,000,000
Net (gain) loss on securities | $	0		$ 1,000,000	1,000,000	$ 2,000,000
Debt securities, available-for-sale | $	$ 8,723,000,000			$ 8,723,000,000			$ 9,060,000,000
Signature Bank | Corporate bonds
Schedule of Investments [Line Items]
Debt securities, available-for-sale | $						$ 20,000,000
Collateralized Debt Obligations
Schedule of Investments [Line Items]
Number of securities continuous unrealized loss position more than twelve months	63			63			23
Capital trust notes
Schedule of Investments [Line Items]
Number of securities continuous unrealized loss position more than twelve months	6			6			5
Asset-backed securities
Schedule of Investments [Line Items]
Number of securities continuous unrealized loss position more than twelve months	9			9			7
Corporate bonds
Schedule of Investments [Line Items]
Number of securities continuous unrealized loss position more than twelve months	13			13			2
Corporate bonds | Signature Bank
Schedule of Investments [Line Items]
Provision for credit loss | $		$ 20,000,000
US Government Agencies Debt Securities
Schedule of Investments [Line Items]
Number of securities continuous unrealized loss position more than twelve months	41			41			33
Agency - commercial
Schedule of Investments [Line Items]
Number of securities continuous unrealized loss position more than twelve months	302			302			133
Mutual funds and common stock
Schedule of Investments [Line Items]
Number of securities continuous unrealized loss position more than twelve months	1			1			1
Municipal bonds
Schedule of Investments [Line Items]
Number of securities continuous unrealized loss position more than twelve months	1			1			1
Foreign notes
Schedule of Investments [Line Items]
Number of securities continuous unrealized loss position more than twelve months	1			1
Federal Home Loan Bank of New York
Schedule of Investments [Line Items]
Federal home loan bank stock | $	$ 578,000,000			$ 578,000,000			$ 762,000,000
Federal Home Loan Bank of Indianapolis
Schedule of Investments [Line Items]
Federal home loan bank stock | $	$ 329,000,000			$ 329,000,000			$ 329,000,000