Commitments and Contingencies - Narrative (Details) - USD ($)	1 Months Ended		3 Months Ended		9 Months Ended
	Aug. 31, 2023	May 31, 2023	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	May 04, 2023	Dec. 31, 2022	Jul. 01, 2021
Loss Contingencies [Line Items]
Reduction in deposit balance over 12 month period									$ 10,000,000,000
Additions (reductions) in deposit balance					$ 0
ID balance ceiling amount above fixed-rate obligation							$ 30,000,000,000
IDA balance floor amount							60,000,000,000
ID balance ceiling amount							90,000,000,000
Percentage of fixed rate investments									80.00%
Maximum buy down in fixed-rate obligation IDA balance							$ 5,000,000,000
Buy down of fixed-rate obligation amounts in deposits balance	$ 2,100,000,000	$ 2,400,000,000
Market-based fee capitalized as a contract asset	$ 115,000,000	$ 112,000,000
Ending IDA balance			$ 99,600,000,000		99,600,000,000			$ 122,600,000,000
Fixed-rate obligation IDA balance			88,700,000,000		88,700,000,000			108,500,000,000
Floating-rate obligation IDA balance			10,900,000,000		10,900,000,000			$ 14,100,000,000
Guarantees
Loss Contingencies [Line Items]
Liability for guarantees			0		0
Residential real estate | First Mortgages
Loss Contingencies [Line Items]
Purchased during period			765,000,000	$ 1,300,000,000	2,400,000,000	$ 6,000,000,000.0
Residential real estate | HELOCs
Loss Contingencies [Line Items]
Purchased during period			$ 49,000,000	$ 92,000,000	$ 144,000,000	$ 252,000,000