Asset-Backed Financing - Assets And Liabilities Of Variable Interest Entities (Details) - USD ($) $ in Thousands	Sep. 29, 2019	Dec. 31, 2018	Sep. 30, 2018
Finance receivables
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	$ 1,771,116	$ 972,080	$ 646,842
Transfers accounted for as secured borrowings, assets, allowance for credit losses, carrying amount	(48,400)	(26,554)	(17,142)
Finance receivables | Asset-backed securitizations | Consolidated VIEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	929,773	158,718	190,461
Transfers accounted for as secured borrowings, assets, allowance for credit losses, carrying amount	(27,517)	(4,691)	(5,634)
Finance receivables | Asset-backed U.S. commercial paper conduit facilities | Consolidated VIEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	599,099	631,588	282,986
Transfers accounted for as secured borrowings, assets, allowance for credit losses, carrying amount	(17,701)	(18,733)	(8,393)
Finance receivables | Asset-backed Canadian commercial paper conduit facility | Unconsolidated VIEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	242,244	181,774	173,395
Transfers accounted for as secured borrowings, assets, allowance for credit losses, carrying amount	(3,182)	(3,130)	(3,115)
Restricted cash
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	86,742	55,982	43,019
Restricted cash | Asset-backed securitizations | Consolidated VIEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	45,096	17,191	18,508
Restricted cash | Asset-backed U.S. commercial paper conduit facilities | Consolidated VIEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	33,238	30,012	15,218
Restricted cash | Asset-backed Canadian commercial paper conduit facility | Unconsolidated VIEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	8,408	8,779	9,293
Other assets
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	1,876	1,906	1,732
Other assets | Asset-backed securitizations | Consolidated VIEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	469	329	437
Other assets | Asset-backed U.S. commercial paper conduit facilities | Consolidated VIEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	1,149	1,234	971
Other assets | Asset-backed Canadian commercial paper conduit facility | Unconsolidated VIEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	258	343	324
Total assets
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	1,811,334	1,003,414	674,451
Total assets | Asset-backed securitizations | Consolidated VIEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	947,821	171,547	203,772
Total assets | Asset-backed U.S. commercial paper conduit facilities | Consolidated VIEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	615,785	644,101	290,782
Total assets | Asset-backed Canadian commercial paper conduit facility | Unconsolidated VIEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	247,728	187,766	179,897
Asset-backed debt
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, associated liabilities, carrying amount	1,553,996	833,835	542,936
Asset-backed debt | Asset-backed securitizations | Consolidated VIEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, associated liabilities, carrying amount	872,871	95,167	128,474
Asset-backed debt | Asset-backed U.S. commercial paper conduit facilities | Consolidated VIEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, associated liabilities, carrying amount	552,757	582,717	265,044
Asset-backed debt | Asset-backed Canadian commercial paper conduit facility | Unconsolidated VIEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, associated liabilities, carrying amount	$ 128,368	$ 155,951	$ 149,418