Derivative and Hedging Activities - Notional Amount and Fair Value of Derivative Financial Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Derivatives designated hedging instruments: | Cash flow hedging
Liabilities
Notional Amount	$ 5,500	$ 3,750
Derivatives designated hedging instruments: | Other Assets | Cash flow hedging
Liabilities
Fair Value	0	5
Derivatives designated hedging instruments: | Other Liabilities | Cash flow hedging
Liabilities
Fair Value	7	0
Derivatives designated hedging instruments: | Interest rate swap on FHLB advances
Liabilities
Fair Value	7	5
Derivatives designated hedging instruments: | Interest rate swap on FHLB advances | Cash flow hedging
Liabilities
Notional Amount	5,500	3,750
Derivatives designated hedging instruments: | Interest rate swap on FHLB advances | Other Assets | Cash flow hedging
Liabilities
Fair Value	0	5
Derivatives designated hedging instruments: | Interest rate swap on FHLB advances | Other Liabilities | Cash flow hedging
Liabilities
Fair Value	7	0
Derivatives designated hedging instruments: | Interest rate swap on multi-family loans held for investment
Liabilities
Fair Value	2
Derivatives designated hedging instruments: | Interest rate swap on multi-family loans held for investment | Fair value hedging
Liabilities
Notional Amount	2,000
Derivatives designated hedging instruments: | Interest rate swap on multi-family loans held for investment | Other Assets | Fair value hedging
Liabilities
Fair Value	0
Derivatives designated hedging instruments: | Interest rate swap on multi-family loans held for investment | Other Liabilities | Fair value hedging
Liabilities
Fair Value	2
Derivatives not designated as hedging instruments:
Assets
Fair Value	164	220
Liabilities
Fair Value	64	126
Derivatives not designated as hedging instruments: | Other Assets
Assets
Notional Amount	9,823	11,403
Fair Value	179	229
Liabilities
Fair Value	0	0
Derivatives not designated as hedging instruments: | Other Liabilities
Assets
Fair Value	0	0
Liabilities
Notional Amount	3,931	3,711
Fair Value	70	136
Derivatives not designated as hedging instruments: | Futures
Assets
Fair Value	0	2
Liabilities
Fair Value	1
Derivatives not designated as hedging instruments: | Futures | Other Assets
Assets
Notional Amount	0	1,205
Fair Value		2
Derivatives not designated as hedging instruments: | Futures | Other Liabilities
Assets
Fair Value	0	0
Derivatives not designated as hedging instruments: | Mortgage-backed securities forwards
Assets
Fair Value	5	36
Liabilities
Fair Value	14	61
Derivatives not designated as hedging instruments: | Mortgage-backed securities forwards | Other Assets
Assets
Notional Amount	542	1,065
Fair Value	5	36
Liabilities
Fair Value	0	0
Derivatives not designated as hedging instruments: | Mortgage-backed securities forwards | Other Liabilities
Assets
Fair Value	0	0
Liabilities
Notional Amount	1,466	739
Fair Value	14	61
Derivatives not designated as hedging instruments: | Rate lock commitments | Other Assets
Assets
Notional Amount	1,759	1,539
Fair Value	15	9
Liabilities
Fair Value	0	0
Derivatives not designated as hedging instruments: | Rate lock commitments | Other Liabilities
Assets
Fair Value	0	0
Liabilities
Notional Amount	218	527
Fair Value	7	10
Derivatives not designated as hedging instruments: | Interest rate swaps and swaptions | Other Assets
Assets
Notional Amount	7,522	7,594
Fair Value	159	182
Liabilities
Fair Value	0	0
Derivatives not designated as hedging instruments: | Interest rate swaps and swaptions | Other Liabilities
Assets
Fair Value	0	0
Liabilities
Notional Amount	2,247	2,445
Fair Value	$ 49	$ 65