Derivative and Hedging Activities - Derivatives Subject to a Master Netting Arrangement (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Derivatives designated as hedging instruments: | Interest rate swaps | Interest rate swaps (fair value hedge)
Assets
Gross Amounts Not Offset in the Statements of Condition	$ 0
Cash Collateral Pledged (Received)	65
Derivatives designated as hedging instruments: | Interest rate swaps | Interest rate caps (cash flow hedge)
Assets
Gross Amounts Not Offset in the Statements of Condition	0
Cash Collateral Pledged (Received)	0
Derivatives not designated as hedging instruments:
Assets
Gross Amounts Not Offset in the Statements of Condition	20	$ 22
Cash Collateral Pledged (Received)	0	(5)
Liabilities
Gross Amounts Not Offset in the Statements of Condition	22	32
Cash Collateral Pledged (Received)	41	57
Derivatives not designated as hedging instruments: | Interest rate swaps
Liabilities
Gross Amounts Not Offset in the Statements of Condition	21	30
Cash Collateral Pledged (Received)	40	47
Derivatives not designated as hedging instruments: | Interest rate swaptions
Assets
Gross Amounts Not Offset in the Statements of Condition	20	15
Cash Collateral Pledged (Received)	0	(3)
Derivatives not designated as hedging instruments: | Mortgage-backed securities forwards
Assets
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	1	2
Cash Collateral Pledged (Received)	$ 1	$ 10