Summary of Significant Accounting Policies - Narrative (Details) $ in Millions		12 Months Ended
	Jan. 01, 2020 USD ($)	Dec. 31, 2019 payment	Dec. 31, 2018 USD ($)	Jan. 01, 2019 USD ($)
Summary of Significant Accounting Policies [Line Items]
Probable loss experience period		10 years
Extension term		6 months
Threshold period for resuming interest accrual on delinquent accounts		60 days
Threshold for delinquent accounts		90 days
Operating lease right-of-use asset				$ 129
Operating lease liabilities				$ 144
Adoption of accounting standards			$ 40
Minimum [Member]
Summary of Significant Accounting Policies [Line Items]
Estimated useful life (in years)		1 year
Maximum [Member]
Summary of Significant Accounting Policies [Line Items]
Estimated useful life (in years)		30 years
Retail Finance Receivables [Member]
Summary of Significant Accounting Policies [Line Items]
Contractually delinquent period		120 days
Number of delinquent payments that can be moved | payment		2
Commercial Finance Receivables [Member]
Summary of Significant Accounting Policies [Line Items]
Typical repayment period		90 days
Contractually delinquent period		360 days
Commercial Finance Receivables [Member] | Maximum [Member]
Summary of Significant Accounting Policies [Line Items]
Payment period after loan is called		60 days
Retained Earnings [Member]
Summary of Significant Accounting Policies [Line Items]
Adoption of accounting standards			$ 40
Retained Earnings [Member] | Forecast [Member] | Accounting Standards Update 2016-13 [Member] | Minimum [Member]
Summary of Significant Accounting Policies [Line Items]
Adoption of accounting standards	$ 600
Financing Receivable, Allowance for Credit Loss [Member] | Forecast [Member] | Accounting Standards Update 2016-13 [Member] | Minimum [Member]
Summary of Significant Accounting Policies [Line Items]
Adoption of accounting standards	$ 800