Finance Receivables - Allowance For Credit Losses And Finance Receivables By Portfolio, Individually And Collectively Evaluated For Impairment (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated for impairment	$ 2,100	$ 0
Collectively evaluated for impairment	196,481	189,885
Total allowance for credit losses	198,581	189,885	$ 192,471	$ 173,343	$ 147,178
Individually evaluated for impairment	4,601	0
Collectively evaluated for impairment	7,568,346	7,411,816
Total finance receivables	7,572,947	7,411,816	7,157,557	7,008,801	7,015,331
Retail
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	188,501	182,098
Total allowance for credit losses	188,501	182,098	186,254	166,810
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	6,416,428	6,328,201
Total finance receivables	6,416,428	6,328,201	6,140,600	5,982,211	5,991,471
Wholesale
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated for impairment	2,100	0
Collectively evaluated for impairment	7,980	7,787
Total allowance for credit losses	10,080	7,787	6,217	6,533
Individually evaluated for impairment	4,601	0
Collectively evaluated for impairment	1,151,918	1,083,615
Total finance receivables	$ 1,156,519	$ 1,083,615	$ 1,016,957	$ 1,026,590	$ 1,023,860