Derivative and Hedging Activities - Derivatives Subject to a Master Netting Arrangement (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Derivatives designated hedging instruments: | Interest rate swaps on FHLB advances
Liabilities
Gross Amount	$ 5	$ 5
Gross Amounts Netted in the Statements of Condition	0	0
Net Amount Presented in the Statements of Condition	5	5
Financial Instruments	4	4
Cash Collateral Pledged (Received)	80	27
Derivatives designated hedging instruments: | Interest rate swaps on multi-family loans held for investment
Liabilities
Gross Amount	1
Gross Amounts Netted in the Statements of Condition	0
Net Amount Presented in the Statements of Condition	1
Financial Instruments	0
Cash Collateral Pledged (Received)	31
Derivatives not designated as hedging instruments:
Assets
Gross Amount	178	220
Gross Amounts Netted in the Statements of Condition	0	0
Net Amount Presented in the Statements of Condition	178	220
Financial Instruments	0	0
Cash Collateral Pledged (Received)	(42)	(44)
Liabilities
Gross Amount	95	126
Gross Amounts Netted in the Statements of Condition	0	0
Net Amount Presented in the Statements of Condition	95	126
Financial Instruments	0	0
Cash Collateral Pledged (Received)	57	83
Derivatives not designated as hedging instruments: | Mortgage-backed securities forwards
Assets
Gross Amount	37	36
Gross Amounts Netted in the Statements of Condition	0	0
Net Amount Presented in the Statements of Condition	37	36
Financial Instruments	0	0
Cash Collateral Pledged (Received)	(6)	(9)
Liabilities
Gross Amount	16	61
Gross Amounts Netted in the Statements of Condition	0	0
Net Amount Presented in the Statements of Condition	16	61
Financial Instruments	0	0
Cash Collateral Pledged (Received)	15	54
Derivatives not designated as hedging instruments: | Interest rate swaptions
Assets
Gross Amount	140	182
Gross Amounts Netted in the Statements of Condition	0	0
Net Amount Presented in the Statements of Condition	140	182
Financial Instruments	0	0
Cash Collateral Pledged (Received)	(37)	(36)
Derivatives not designated as hedging instruments: | Futures
Assets
Gross Amount	1	2
Gross Amounts Netted in the Statements of Condition	0
Net Amount Presented in the Statements of Condition	1	2
Financial Instruments	0
Cash Collateral Pledged (Received)	1	1
Liabilities
Gross Amount	0
Gross Amounts Netted in the Statements of Condition	0
Net Amount Presented in the Statements of Condition	0
Financial Instruments	0
Cash Collateral Pledged (Received)	0
Derivatives not designated as hedging instruments: | Interest rate swaps
Liabilities
Gross Amount	79	65
Gross Amounts Netted in the Statements of Condition	0	0
Net Amount Presented in the Statements of Condition	79	65
Financial Instruments	0	0
Cash Collateral Pledged (Received)	$ 42	$ 29