Asset-Backed Financing (Assets And Liabilities Of Variable Interest Entities) (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 24, 2017
Finance receivables
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	$ 646,842	$ 943,522	$ 949,253
Finance receivables | Asset-backed securitizations | SPEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	190,461	439,301	511,643
Finance receivables | Asset-backed U.S. commercial paper conduit facilities | SPEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	282,986	300,530	298,197
Finance receivables | Asset-backed Canadian commercial paper conduit facility | Variable Interest Entity, Not Primary Beneficiary
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	173,395	203,691	139,413
Allowance for credit losses
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	(17,142)	(26,824)	(27,591)
Allowance for credit losses | Asset-backed securitizations | SPEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	(5,634)	(13,686)	(15,798)
Allowance for credit losses | Asset-backed U.S. commercial paper conduit facilities | SPEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	(8,393)	(9,392)	(9,233)
Allowance for credit losses | Asset-backed Canadian commercial paper conduit facility | Variable Interest Entity, Not Primary Beneficiary
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	(3,115)	(3,746)	(2,560)
Restricted cash
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	43,019	58,689	63,380
Restricted cash | Asset-backed securitizations | SPEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	18,508	34,919	40,385
Restricted cash | Asset-backed U.S. commercial paper conduit facilities | SPEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	15,218	13,787	14,922
Restricted cash | Asset-backed Canadian commercial paper conduit facility | Variable Interest Entity, Not Primary Beneficiary
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	9,293	9,983	8,073
Other assets
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	1,732	2,618	2,790
Other assets | Asset-backed securitizations | SPEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	437	1,260	1,513
Other assets | Asset-backed U.S. commercial paper conduit facilities | SPEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	971	888	927
Other assets | Asset-backed Canadian commercial paper conduit facility | Variable Interest Entity, Not Primary Beneficiary
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	324	470	350
Total assets
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	674,451	978,005	987,832
Total assets | Asset-backed securitizations | SPEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	203,772	461,794	537,743
Total assets | Asset-backed U.S. commercial paper conduit facilities | SPEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	290,782	305,813	304,813
Total assets | Asset-backed Canadian commercial paper conduit facility | Variable Interest Entity, Not Primary Beneficiary
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	179,897	210,398	145,276
Asset-backed debt
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, associated liabilities, carrying amount	542,936	806,860	832,271
Asset-backed debt | Asset-backed securitizations | SPEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, associated liabilities, carrying amount	128,474	352,624	429,833
Asset-backed debt | Asset-backed U.S. commercial paper conduit facilities | SPEs
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, associated liabilities, carrying amount	265,044	279,457	280,308
Asset-backed debt | Asset-backed Canadian commercial paper conduit facility | Variable Interest Entity, Not Primary Beneficiary
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, associated liabilities, carrying amount	$ 149,418	$ 174,779	$ 122,130