Finance Receivables - Credit Risk Profile by Dealer grouping of Commercial Finance Receivables (Details) - Commercial Finance Receivables [Member] - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at end of period	$ 9,760	$ 8,439	$ 7,845	$ 8,072
Percent of portfolio (percent)	100.00%	100.00%
Group I [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at end of period	$ 1,531	$ 1,299
Percent of portfolio (percent)	15.70%	15.40%
Group II [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at end of period	$ 3,026	$ 2,648
Percent of portfolio (percent)	31.00%	31.40%
Group III [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at end of period	$ 3,282	$ 2,703
Percent of portfolio (percent)	33.60%	32.00%
Group IV [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at end of period	$ 1,164	$ 1,100
Percent of portfolio (percent)	11.90%	13.00%
Group V [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at end of period	$ 611	$ 505
Percent of portfolio (percent)	6.30%	6.00%
Group VI [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at end of period	$ 146	$ 184
Percent of portfolio (percent)	1.50%	2.20%