Finance Receivables - Investment Of Wholesale Finance Receivables By Internal And External Credit Quality Indicator (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, gross	$ 7,572,947	$ 7,411,816	$ 7,157,557	$ 7,008,801	$ 7,015,331
Retail
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, gross	6,416,428	6,328,201	6,140,600	5,982,211	5,991,471
Retail | Prime
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, gross	5,278,093	5,183,754
Retail | Sub-prime
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, gross	1,138,335	1,144,447
Wholesale
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, gross	1,156,519	1,083,615	$ 1,016,957	$ 1,026,590	$ 1,023,860
Wholesale | Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, gross	11,664	2,210
Wholesale | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, gross	6,122	9,660
Wholesale | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, gross	16,125	10,299
Wholesale | Medium Risk
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, gross	16,800	25,802
Wholesale | Low Risk
Financing Receivable, Credit Quality Indicator [Line Items]
Financing receivable, gross	$ 1,105,808	$ 1,035,644