Finance Receivables - Allowance For Credit Losses And Finance Receivables By Portfolio, Individually And Collectively Evaluated For Impairment (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated for impairment		$ 2,100
Collectively evaluated for impairment		196,481
Total allowance for credit losses	$ 390,936	198,581	$ 189,885	$ 192,471	$ 173,343
Individually evaluated for impairment		4,601
Collectively evaluated for impairment		7,568,346
Total financing receivables	6,833,944	7,572,947	7,411,816	7,157,557	7,008,801
Retail
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated for impairment		0
Collectively evaluated for impairment		188,501
Total allowance for credit losses	371,738	188,501	182,098	186,254
Individually evaluated for impairment		0
Collectively evaluated for impairment		6,416,428
Total financing receivables	6,344,195	6,416,428	6,328,201	6,140,600	5,982,211
Wholesale
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually evaluated for impairment		2,100
Collectively evaluated for impairment		7,980
Total allowance for credit losses	19,198	10,080	7,787	6,217
Individually evaluated for impairment		4,601
Collectively evaluated for impairment		1,151,918
Total financing receivables	$ 489,749	$ 1,156,519	$ 1,083,615	$ 1,016,957	$ 1,026,590