Derivative and Hedging Activities and Restricted Cash - Derivatives Subject to a Master Netting Arrangement (Details) - Derivatives not designated as hedging instruments: - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Derivative Asset [Abstract]
Gross Amounts Not Offset in the Statements of Condition	$ 15	$ 22
Cash Collateral Pledged (Received)	0	(5)
Liabilities
Gross Amounts Not Offset in the Statements of Condition	26	32
Cash Collateral Pledged (Received)	34	57
Mortgage-backed securities forwards
Derivative Asset [Abstract]
Gross Amounts Not Offset in the Statements of Condition		7
Cash Collateral Pledged (Received)		(2)
Liabilities
Gross Amounts Not Offset in the Statements of Condition	3	2
Cash Collateral Pledged (Received)	30	10
Interest rate swaptions
Derivative Asset [Abstract]
Gross Amounts Not Offset in the Statements of Condition	15	15
Cash Collateral Pledged (Received)	0	(3)
Interest rate swaps
Liabilities
Gross Amounts Not Offset in the Statements of Condition	23	30
Cash Collateral Pledged (Received)	$ 4	$ 47