Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			$ (116)
Amounts reclassified in period to Condensed Statements of Income:
Ending balance	$ 125		125
Total in AOCI
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	105	$ (246)	(116)	$ (88)
Other comprehensive income before reclassification - recorded to the Condensed Statements of Condition	31	204	264	56
Amounts reclassified in period to Condensed Statements of Income:
Net interest income	(11)	(11)	(22)	(20)
Noninterest expense	0		(1)	(1)
Ending balance	125	(53)	125	(53)
Net Unrealized -Available-for-sale Debt Securities | Net Unrealized -Available-for-sale Debt Securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	18	(341)	(198)	(179)
Other comprehensive income before reclassification - recorded to the Condensed Statements of Condition	25	182	241	20
Amounts reclassified in period to Condensed Statements of Income:
Net interest income	0	0	0	0
Ending balance	43	(159)	43	(159)
Net Unrealized - Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	79	85	72	102
Other comprehensive income before reclassification - recorded to the Condensed Statements of Condition	6	22	24	14
Amounts reclassified in period to Condensed Statements of Income:
Net interest income	(11)	(11)	(22)	(20)
Ending balance	74	96	74	96
Post - Retirement Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	8	10	10	(11)
Other comprehensive income before reclassification - recorded to the Condensed Statements of Condition	0	0	(1)	22
Amounts reclassified in period to Condensed Statements of Income:
Noninterest expense	0		(1)	(1)
Ending balance	$ 8	$ 10	$ 8	$ 10