Finance Receivables - Credit Risk Profile by Dealer grouping of Commercial Finance Receivables (Details) - Commercial Finance Receivables [Member] - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at end of period	$ 11,812	$ 11,123
Percent of portfolio (percent)	100.00%	100.00%
Group I [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at end of period	$ 1,664	$ 1,596
Percent of portfolio (percent)	14.10%	14.30%
Group II [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at end of period	$ 3,804	$ 3,445
Percent of portfolio (percent)	32.20%	31.00%
Group III [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at end of period	$ 4,171	$ 4,039
Percent of portfolio (percent)	35.30%	36.30%
Group IV [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at end of period	$ 1,441	$ 1,231
Percent of portfolio (percent)	12.20%	11.10%
Group V [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at end of period	$ 548	$ 642
Percent of portfolio (percent)	4.60%	5.80%
Group VI [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at end of period	$ 184	$ 170
Percent of portfolio (percent)	1.60%	1.50%