Finance Receivables - Aging Of Past Due Finance Receivables Including Non-Accrual Status Finance Receivables (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Past Due [Line Items]
Financing receivable, not past due	$ 6,653,925	$ 7,324,346
Financing receivable, past due	180,019	248,601
Total financing receivables	6,833,944	7,572,947	$ 7,411,816	$ 7,157,557	$ 7,008,801
31-60 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, past due	106,984	143,624
61-90 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, past due	39,956	54,379
Greater than 90 days past due
Financing Receivable, Past Due [Line Items]
Financing receivable, past due	33,079	50,598
Retail
Financing Receivable, Past Due [Line Items]
Financing receivable, not past due	6,164,369	6,171,930
Financing receivable, past due	179,826	244,498
Total financing receivables	6,344,195	6,416,428	6,328,201	6,140,600	5,982,211
Retail | 31-60 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, past due	106,818	142,479
Retail | 61-90 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, past due	39,933	53,995
Retail | Greater than 90 days past due
Financing Receivable, Past Due [Line Items]
Financing receivable, past due	33,075	48,024
Wholesale
Financing Receivable, Past Due [Line Items]
Financing receivable, not past due	489,556	1,152,416
Financing receivable, past due	193	4,103
Total financing receivables	489,749	1,156,519	$ 1,083,615	$ 1,016,957	$ 1,026,590
Wholesale | 31-60 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, past due	166	1,145
Wholesale | 61-90 Days Past Due
Financing Receivable, Past Due [Line Items]
Financing receivable, past due	23	384
Wholesale | Greater than 90 days past due
Financing Receivable, Past Due [Line Items]
Financing receivable, past due	$ 4	$ 2,574