Asset-Backed Financing - Assets And Liabilities Of Variable Interest Entities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Total assets
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounts for as secured borrowings, assets, carrying amount	$ 1,622,750	$ 1,003,414
Total assets | Term asset-backed securitizations | Consolidated VIEs:
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounts for as secured borrowings, assets, carrying amount	837,927	171,547
Total assets | Asset-backed U.S. commercial paper conduit facility | Consolidated VIEs:
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounts for as secured borrowings, assets, carrying amount	546,928	644,101
Total assets | Asset-backed Canadian commercial paper conduit facility | Unconsolidated VIEs:
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounts for as secured borrowings, assets, carrying amount	237,895	187,766
Finance receivables
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounts for as secured borrowings, assets, carrying amount	1,592,333	972,080
Finance receivables | Term asset-backed securitizations | Consolidated VIEs:
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounts for as secured borrowings, assets, carrying amount	826,047	158,718
Finance receivables | Asset-backed U.S. commercial paper conduit facility | Consolidated VIEs:
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounts for as secured borrowings, assets, carrying amount	533,587	631,588
Finance receivables | Asset-backed Canadian commercial paper conduit facility | Unconsolidated VIEs:
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounts for as secured borrowings, assets, carrying amount	232,699	181,774
Allowance for credit losses
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounts for as secured borrowings, assets, allowance for loan losses, carrying amount	(43,797)	(26,554)
Allowance for credit losses | Term asset-backed securitizations | Consolidated VIEs:
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounts for as secured borrowings, assets, allowance for loan losses, carrying amount	(24,935)	(4,691)
Allowance for credit losses | Asset-backed U.S. commercial paper conduit facility | Consolidated VIEs:
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounts for as secured borrowings, assets, allowance for loan losses, carrying amount	(16,076)	(18,733)
Allowance for credit losses | Asset-backed Canadian commercial paper conduit facility | Unconsolidated VIEs:
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounts for as secured borrowings, assets, allowance for loan losses, carrying amount	(2,786)	(3,130)
Restricted cash
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounts for as secured borrowings, assets, carrying amount	71,498	55,982
Restricted cash | Term asset-backed securitizations | Consolidated VIEs:
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounts for as secured borrowings, assets, carrying amount	36,037	17,191
Restricted cash | Asset-backed U.S. commercial paper conduit facility | Consolidated VIEs:
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounts for as secured borrowings, assets, carrying amount	27,775	30,012
Restricted cash | Asset-backed Canadian commercial paper conduit facility | Unconsolidated VIEs:
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounts for as secured borrowings, assets, carrying amount	7,686	8,779
Other assets
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounts for as secured borrowings, assets, carrying amount	2,716	1,906
Other assets | Term asset-backed securitizations | Consolidated VIEs:
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounts for as secured borrowings, assets, carrying amount	778	329
Other assets | Asset-backed U.S. commercial paper conduit facility | Consolidated VIEs:
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounts for as secured borrowings, assets, carrying amount	1,642	1,234
Other assets | Asset-backed Canadian commercial paper conduit facility | Unconsolidated VIEs:
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounts for as secured borrowings, assets, carrying amount	296	343
Asset-backed debt
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounts for as secured borrowings, liabilities, carrying amount	1,369,512	833,835
Asset-backed debt | Term asset-backed securitizations | Consolidated VIEs:
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounts for as secured borrowings, liabilities, carrying amount	764,392	95,167
Asset-backed debt | Asset-backed U.S. commercial paper conduit facility | Consolidated VIEs:
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounts for as secured borrowings, liabilities, carrying amount	490,427	582,717
Asset-backed debt | Asset-backed Canadian commercial paper conduit facility | Unconsolidated VIEs:
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers accounts for as secured borrowings, liabilities, carrying amount	$ 114,693	$ 155,951