Description of Business, Basis of Presentation, and Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2023 USD ($) segment	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of loan portfolio segments | segment	4
Operating lease impairment loss	$ 0	$ 0	$ 0
Opening retained earnings	13,766,000,000	12,859,000,000	17,050,000,000	$ 14,703,000,000
Retained earnings (accumulated deficit)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Opening retained earnings	$ 154,000,000	$ (384,000,000)	$ (1,599,000,000)	$ (4,278,000,000)
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Useful life	3 years
Minimum | Capitalized software
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Useful life	3 years
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Useful life	30 years
Maximum | Capitalized software
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Useful life	5 years