Asset-Backed Financing (Assets And Liabilities Of Variable Interest Entities) (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Apr. 01, 2018
Finance receivables
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	$ 794,845	$ 972,080	$ 849,975
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	62,771	158,718	367,584
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	567,295	631,588	299,318
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	164,779	181,774	183,073
Allowance for credit losses
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	(21,679)	(26,554)	(23,769)
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	(1,855)	(4,691)	(11,387)
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	(16,821)	(18,733)	(9,297)
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	(3,003)	(3,130)	(3,085)
Restricted cash
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	49,531	55,982	65,740
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	8,199	17,191	38,207
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	31,565	30,012	16,933
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	9,767	8,779	10,600
Other assets
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	1,698	1,906	2,495
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	134	329	1,207
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	1,282	1,234	968
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	282	343	320
Total assets
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, assets, carrying amount	824,395	1,003,414	894,441
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	69,249	171,547	395,611
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	583,321	644,101	307,922
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	171,825	187,766	190,908
Asset-backed debt
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings
Transfers accounts for as secured borrowings, associated liabilities, carrying amount	688,317	833,835	724,266
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	18,694	95,167	284,793
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	526,947	582,717	281,311
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	$ 142,676	$ 155,951	$ 158,162