Finance Receivables (Finance Receivables) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, gross	$ 7,157,557	$ 7,008,801	$ 7,015,331	$ 6,560,245	$ 6,110,256
Allowance for credit losses	(192,471)	(173,343)	(147,178)	(127,364)	(110,693)
Total finance receivables, net	6,965,086	6,835,458	6,868,153	6,432,881	5,999,563
United States
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, gross	6,840,623
Canada
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, gross	316,934
Wholesale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, gross	1,016,957	1,026,590	1,023,860	952,321	845,212
Allowance for credit losses	(6,217)	(6,533)	(7,858)	(5,339)
Wholesale | United States
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, gross	939,621	961,150	965,379	903,380	800,491
Wholesale | Canada
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, gross	77,336	65,440	58,481	48,941	44,721
Retail
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, gross	6,140,600	5,982,211	5,991,471	5,607,924	5,265,044
Allowance for credit losses	(186,254)	(166,810)	(139,320)	(122,025)
Retail | United States
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, gross	5,901,002	5,769,410	5,803,071	5,398,006	5,051,245
Retail | Canada
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, gross	$ 239,598	$ 212,801	$ 188,400	$ 209,918	$ 213,799