Commitments and Contingencies - Narrative (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	May 04, 2023
Loss Contingencies [Line Items]
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
Buy down of fixed-rate obligation amounts in deposits balance			$ 5,000,000,000
Market-based fee capitalized as a contract asset			249,000,000
Ending IDA balance	90,300,000,000		97,500,000,000
Fixed-rate obligation IDA balance	79,200,000,000		83,700,000,000
Floating-rate obligation IDA balance	11,100,000,000		$ 13,800,000,000
Guarantees
Loss Contingencies [Line Items]
Liability for guarantees	0
Residential real estate | First Mortgages
Loss Contingencies [Line Items]
Purchased during period	680,000,000	$ 723,000,000
Residential real estate | HELOCs
Loss Contingencies [Line Items]
Purchased during period	$ 36,000,000	$ 43,000,000