Finance Receivables (Allowance For Credit Losses And Finance Receivables By Portfolio Individually And Collectively Evaluated For Impairment) (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Apr. 01, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses
Individually evaluated for impairment	$ 0	$ 0	$ 184
Collectively evaluated for impairment	190,872	189,885	190,166
Total allowance for credit losses	190,872	189,885	190,350	$ 192,471
Individually evaluated for impairment	0	0	220
Collectively evaluated for impairment	7,629,464	7,411,816	7,316,572
Financing receivable, gross	7,629,464	7,411,816	7,316,792
Retail
Financing Receivable, Allowance for Credit Losses
Individually evaluated for impairment	0	0	0
Collectively evaluated for impairment	181,426	182,098	182,150
Total allowance for credit losses	181,426	182,098	182,150	186,254
Individually evaluated for impairment	0	0	0
Collectively evaluated for impairment	6,290,036	6,328,201	6,064,192
Financing receivable, gross	6,290,036	6,328,201	6,064,192
Wholesale
Financing Receivable, Allowance for Credit Losses
Individually evaluated for impairment	0	0	184
Collectively evaluated for impairment	9,446	7,787	8,016
Total allowance for credit losses	9,446	7,787	8,200	$ 6,217
Individually evaluated for impairment	0	0	220
Collectively evaluated for impairment	1,339,428	1,083,615	1,252,380
Financing receivable, gross	$ 1,339,428	$ 1,083,615	$ 1,252,600

A valuation allowance for financing receivables that are expected to be uncollectible.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

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- Definition

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

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- Definition

Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

The balance of financing receivables that were collectively evaluated for impairment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

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- Definition

The balance of financing receivables that were individually evaluated for impairment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

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- Definition

Amount representing an agreement for an unconditional promise by the maker to pay the entity (holder) a definite sum of money at a future date. Such amount may include accrued interest receivable in accordance with the terms of the note. The note also may contain provisions and related items including a discount or premium, payable on demand, secured, or unsecured, interest bearing or noninterest bearing, among a myriad of other features and characteristics. Excludes amounts related to receivables held-for-sale.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.10(3))
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