Derivative and Hedging Activities - Derivatives Subject to a Master Netting Arrangement (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Derivatives designated as cash flow hedging instruments: | Interest rate swaps on FHLB advances
Liabilities
Financial Instruments		$ 2
Cash Collateral Pledged (Received)		75
Derivatives designated as cash flow hedging instruments: | Interest rate swaps on multi-family loans held for investment
Liabilities
Financial Instruments		1
Cash Collateral Pledged (Received)		27
Interest rate swaps on multi-family loans held for investment
Assets
Financial Instruments	$ 22	126
Cash Collateral Pledged (Received)	(5)	(35)
Liabilities
Financial Instruments	32	92
Cash Collateral Pledged (Received)	57	102
Interest rate swaps on multi-family loans held for investment | Mortgage-backed securities forwards
Assets
Financial Instruments	7	11
Cash Collateral Pledged (Received)	(2)	(1)
Liabilities
Financial Instruments	2	32
Cash Collateral Pledged (Received)	10	57
Interest rate swaps on multi-family loans held for investment | Interest rate swaptions
Assets
Financial Instruments	15	115
Cash Collateral Pledged (Received)	(3)	(34)
Interest rate swaps on multi-family loans held for investment | Futures
Liabilities
Financial Instruments		1
Cash Collateral Pledged (Received)		3
Interest rate swaps on multi-family loans held for investment | Interest rate swaps
Liabilities
Financial Instruments	30	59
Cash Collateral Pledged (Received)	$ 47	$ 42