Summary of Significant Accounting Policies - Narrative (Details) $ in Millions		12 Months Ended
	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($) payment	Jan. 01, 2018 USD ($)
Summary of Significant Accounting Policies [Line Items]
Probable loss experience period		10 years
Threshold period for resuming interest accrual on delinquent accounts		60 days
Threshold for delinquent accounts		90 days
Adoption of accounting standards		$ 40
Minimum [Member]
Summary of Significant Accounting Policies [Line Items]
Credit facility expiration period		12 months
Estimated useful life (in years)		1 year
Maximum [Member]
Summary of Significant Accounting Policies [Line Items]
Credit facility expiration period		18 months
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
Accounting Standards Update 2014-09 [Member] | Retained Earnings [Member]
Summary of Significant Accounting Policies [Line Items]
Cumulative effect adjustment			$ 33
Noncancelable Operating Lease Obligations [Member] | Scenario, Forecast [Member] | Accounting Standards Update 2016-02 [Member]
Summary of Significant Accounting Policies [Line Items]
Adoption of accounting standards	$ 140
Noncancelable Operating Lease Assets [Member] | Scenario, Forecast [Member] | Accounting Standards Update 2016-02 [Member]
Summary of Significant Accounting Policies [Line Items]
Adoption of accounting standards	$ 140