Derivative and Hedging Activities - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2023	Dec. 31, 2022
Derivative Instruments, Gain (Loss) [Line Items]
Interest , loans and leases held-for-sale	$ 8	$ 15
Hedged debt, carrying amount	6,400	6,400
Fair value of interest rate fair value hedging instruments		46
Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	2,000	2,000
Interest rate swaps | Derivatives designated hedging instruments:
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	2,000	2,000
Interest rate swaps on FHLB advances | Derivatives designated hedging instruments: | Cash flow hedging
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, notional amount	5,500	5,500	$ 3,800
Unrealized gains on cash flow hedges:
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized losses on derivatives classified as cash flow hedges		110	$ 52
Amount of gain (loss), net of tax, to be reclassified during the next 12 months	$ 124	$ 124