Summary of Significant Accounting Policies - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) segment payment	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Summary of Significant Accounting Policies [Line Items]
Typical repayment period	30 days
Probable loss experience period	10 years
Number of delinquent payments that can be moved | payment	2
Number of additional operating segments | segment	2
Net cash used in operating activities	$ (4,881)	$ (2,168)	$ (1,637)
Net cash used in investing activities	24,774	22,033	10,236
Beginning of period cash and cash equivalents	$ 5,302	5,002	5,045	$ 3,031
North America [Member] | Income Approach Valuation Technique [Member]
Summary of Significant Accounting Policies [Line Items]
Weight applied (percent)	75.00%
North America [Member] | Market Approach Valuation Technique [Member]
Summary of Significant Accounting Policies [Line Items]
Weight applied (percent)	25.00%
North America [Member] | Goodwill [Member]
Summary of Significant Accounting Policies [Line Items]
Concentration risk (percent)	92.00%
Minimum [Member]
Summary of Significant Accounting Policies [Line Items]
Credit facility expiration period	6 months
Estimated useful life (in years)	1 year
Maximum [Member]
Summary of Significant Accounting Policies [Line Items]
Credit facility expiration period	24 months
Estimated useful life (in years)	30 years
Retail Finance Receivables [Member]
Summary of Significant Accounting Policies [Line Items]
Contractually delinquent period	120 days
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
Accounting Standards Update 2016-18 [Member] | Scenario, Adjustment [Member]
Summary of Significant Accounting Policies [Line Items]
Net cash used in operating activities		271
Net cash used in investing activities		264	232
Beginning of period cash and cash equivalents		$ 1,900	$ 2,100	$ 2,000