Derivative and Hedging Activities - Notional Amount and Fair Value of Derivative Financial Instruments (Details) - USD ($) $ in Millions	Jun. 30, 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	1	5
Derivatives designated hedging instruments: | Other Liabilities | Cash flow hedging
Liabilities
Fair Value	0	0
Derivatives designated hedging instruments: | Interest rate swaps on FHLB advances
Liabilities
Fair Value	1	5
Derivatives designated hedging instruments: | Interest rate swaps on FHLB advances | Cash flow hedging
Liabilities
Notional Amount	5,500	3,750
Derivatives designated hedging instruments: | Interest rate swaps on FHLB advances | Other Assets | Cash flow hedging
Liabilities
Fair Value	1	5
Derivatives designated hedging instruments: | Interest rate swaps on FHLB advances | Other Liabilities | Cash flow hedging
Liabilities
Fair Value	0	0
Derivatives designated hedging instruments: | Interest rate swaps on multi-family loans held for investment
Liabilities
Fair Value	0
Derivatives designated hedging instruments: | Interest rate swaps on multi-family loans held for investment | Fair value hedging
Liabilities
Notional Amount	2,000
Derivatives designated hedging instruments: | Interest rate swaps on multi-family loans held for investment | Other Assets | Fair value hedging
Liabilities
Fair Value	0
Derivatives designated hedging instruments: | Interest rate swaps on multi-family loans held for investment | Other Liabilities | Fair value hedging
Liabilities
Fair Value	0
Derivatives not designated as hedging instruments:
Assets
Fair Value	160	220
Liabilities
Fair Value	68	126
Derivatives not designated as hedging instruments: | Other Assets
Assets
Notional Amount	34,095	11,403
Fair Value	170	229
Liabilities
Fair Value	0	0
Derivatives not designated as hedging instruments: | Other Liabilities
Assets
Fair Value	0	0
Liabilities
Notional Amount	20,925	3,711
Fair Value	78	136
Derivatives not designated as hedging instruments: | Futures
Assets
Fair Value	3	2
Liabilities
Fair Value	0
Derivatives not designated as hedging instruments: | Futures | Other Assets
Assets
Notional Amount	2,530	1,205
Fair Value	3	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	21	36
Liabilities
Fair Value	7	61
Derivatives not designated as hedging instruments: | Mortgage-backed securities forwards | Other Assets
Assets
Notional Amount	2,372	1,065
Fair Value	21	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	727	739
Fair Value	7	61
Derivatives not designated as hedging instruments: | Rate lock commitments | Other Assets
Assets
Notional Amount	1,954	1,539
Fair Value	10	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	543	527
Fair Value	10	10
Derivatives not designated as hedging instruments: | Interest rate swaps and swaptions | Other Assets
Assets
Notional Amount	7,414	7,594
Fair Value	136	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	1,442	2,445
Fair Value	61	$ 65
Derivatives not designated as hedging instruments: | Foreign currency swaps | Other Assets
Assets
Notional Amount	19,825
Fair Value	0
Liabilities
Fair Value	0
Derivatives not designated as hedging instruments: | Foreign currency swaps | Other Liabilities
Assets
Fair Value	0
Liabilities
Notional Amount	18,213
Fair Value	$ 0