Finance Receivables (Aging Of Past Due Finance Receivables Including Non-Accrual Status Finance Receivables) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	$ 6,929,473	$ 6,785,813
Total Past Due	228,084	222,988
Total finance receivables	7,157,557	7,008,801	$ 7,015,331	$ 6,560,245	$ 6,110,256
31-60 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	140,224	132,302
61-90 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	47,784	49,961
Greater than 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	40,076	40,725
Retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	5,913,473	5,760,818
Total Past Due	227,127	221,393
Total finance receivables	6,140,600	5,982,211	5,991,471	5,607,924	5,265,044
Retail | 31-60 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	139,629	131,302
Retail | 61-90 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	47,539	49,642
Retail | Greater than 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	39,959	40,449
Wholesale
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	1,016,000	1,024,995
Total Past Due	957	1,595
Total finance receivables	1,016,957	1,026,590	$ 1,023,860	$ 952,321	$ 845,212
Wholesale | 31-60 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	595	1,000
Wholesale | 61-90 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	245	319
Wholesale | Greater than 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 117	$ 276