Investments (AFS Unrealized Losses) (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 0	$ (1)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	3,805	4,516
Debt Securities, Available-for-sale, Unrealized Loss Position	4,096	5,002
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(24)	(28)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	291	486
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(24)	(27)
US Government Agencies Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	2	3
Debt Securities, Available-for-sale, Unrealized Loss Position	5	10
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	3	7
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
State or local housing agency obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	(1)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	157	123
Debt Securities, Available-for-sale, Unrealized Loss Position	224	205
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(1)	(1)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	67	82
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(1)	0
Non-mortgage-backed securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	(1)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	159	126
Debt Securities, Available-for-sale, Unrealized Loss Position	229	215
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(1)	(1)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	70	89
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(1)	0
Mortgage-backed securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	3,646	4,390
Debt Securities, Available-for-sale, Unrealized Loss Position	3,867	4,787
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(23)	(27)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	221	397
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(23)	(27)
Single Family [Member] | U.S. obligations MBS [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	120	488
Debt Securities, Available-for-sale, Unrealized Loss Position	255	669
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	0	(1)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	135	181
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	(1)
Single Family [Member] | Mortgage-backed securities, GSE [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	58	71
Debt Securities, Available-for-sale, Unrealized Loss Position	63	71
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(1)	(1)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	5	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(1)	(1)
Multifamily [Member] | Mortgage-backed securities, GSE [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	3,468	3,831
Debt Securities, Available-for-sale, Unrealized Loss Position	3,549	4,047
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(22)	(25)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	81	216
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (22)	$ (25)