Derivative and Hedging Activities - Derivatives Subject to a Master Netting Arrangement (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Derivatives designated hedging instruments: | Interest rate swaps on FHLB advances
Liabilities
Gross Amount		$ 2
Gross Amounts Netted in the Statements of Condition		0
Net Amount Presented in the Statements of Condition		2
Financial Instruments		0
Cash Collateral Pledged (Received)		75
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)		27
Derivatives not designated as hedging instruments:
Assets
Gross Amount	$ 120	126
Gross Amounts Netted in the Statements of Condition	0	0
Net Amount Presented in the Statements of Condition	120	126
Financial Instruments	0	0
Cash Collateral Pledged (Received)	(3)	(35)
Liabilities
Gross Amount	72	92
Gross Amounts Netted in the Statements of Condition	0	0
Net Amount Presented in the Statements of Condition	72	92
Financial Instruments	0	0
Cash Collateral Pledged (Received)	106	102
Derivatives not designated as hedging instruments: | Mortgage-backed securities forwards
Assets
Gross Amount	9	11
Gross Amounts Netted in the Statements of Condition	0	0
Net Amount Presented in the Statements of Condition	9	11
Financial Instruments	0	0
Cash Collateral Pledged (Received)	0	(1)
Liabilities
Gross Amount	9	32
Gross Amounts Netted in the Statements of Condition	0	0
Net Amount Presented in the Statements of Condition	9	32
Financial Instruments	0	0
Cash Collateral Pledged (Received)	8	57
Derivatives not designated as hedging instruments: | Interest rate swaptions
Assets
Gross Amount	111	115
Gross Amounts Netted in the Statements of Condition	0	0
Net Amount Presented in the Statements of Condition	111	115
Financial Instruments	0	0
Cash Collateral Pledged (Received)	(3)	(34)
Derivatives not designated as hedging instruments: | Futures
Assets
Gross Amount	0
Gross Amounts Netted in the Statements of Condition	0	0
Net Amount Presented in the Statements of Condition	0	0
Financial Instruments	0	0
Cash Collateral Pledged (Received)	0	0
Liabilities
Gross Amount	0	1
Gross Amounts Netted in the Statements of Condition	0	0
Net Amount Presented in the Statements of Condition	0	1
Financial Instruments	0
Cash Collateral Pledged (Received)	1	3
Derivatives not designated as hedging instruments: | Interest rate swaps
Liabilities
Gross Amount	63	59
Gross Amounts Netted in the Statements of Condition	0	0
Net Amount Presented in the Statements of Condition	63	59
Financial Instruments	0	0
Cash Collateral Pledged (Received)	$ 97	$ 42