Asset-Backed Financing - Assets And Liabilities Of Variable Interest Entities (Details) - USD ($) $ in Thousands	Mar. 29, 2020	Dec. 31, 2019	Mar. 31, 2019
Finance receivables
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	$ 2,120,305	$ 1,592,333	$ 794,845
Transfers accounted for as secured borrowings, assets, allowance for credit losses, carrying amount	(101,702)	(43,797)	(21,679)
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	1,250,382	826,047	62,771
Transfers accounted for as secured borrowings, assets, allowance for credit losses, carrying amount	(62,159)	(24,935)	(1,855)
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	662,385	533,587	567,295
Transfers accounted for as secured borrowings, assets, allowance for credit losses, carrying amount	(32,872)	(16,076)	(16,821)
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	207,538	232,699	164,779
Transfers accounted for as secured borrowings, assets, allowance for credit losses, carrying amount	(6,671)	(2,786)	(3,003)
Restricted cash
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	109,787	71,498	49,531
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	61,945	36,037	8,199
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	37,290	27,775	31,565
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	10,552	7,686	9,767
Other assets
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	2,410	2,716	1,698
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	852	778	134
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	1,410	1,642	1,282
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	148	296	282
Total assets
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	2,130,800	1,622,750	824,395
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	1,251,020	837,927	69,249
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	668,213	546,928	583,321
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	211,567	237,895	171,825
Asset-backed debt
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, associated liabilities, carrying amount	1,912,088	1,369,512	688,317
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	1,156,845	764,392	18,694
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	600,000	490,427	526,947
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	$ 155,243	$ 114,693	$ 142,676