Finance Receivables, Credit Quality Information, and Allowance for Credit Losses - Tabular Disclosure of Impaired Financing Receivables (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired receivables specifically evaluated	$ 28,963	$ 26,585
Finance receivables evaluated collectively	883,287	905,658
Finance receivables	912,250	932,243	$ 804,956
Impaired receivables in nonaccrual status	3,549	3,716
Amount of the specific reserve for impaired accounts	11,660	11,204
Amount of the general component of the allowance	44,740	47,096
Small Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired receivables specifically evaluated	9,780	8,361
Finance receivables evaluated collectively	411,932	429,301
Finance receivables	421,712	437,662	360,470
Impaired receivables in nonaccrual status	1,091	1,209
Amount of the specific reserve for impaired accounts	4,334	3,791
Amount of the general component of the allowance	25,459	26,968
Large Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired receivables specifically evaluated	18,241	17,196
Finance receivables evaluated collectively	422,466	420,802
Finance receivables	440,707	437,998	363,931
Impaired receivables in nonaccrual status	2,266	2,292
Amount of the specific reserve for impaired accounts	6,883	6,860
Amount of the general component of the allowance	16,334	16,842
Automobile Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired receivables specifically evaluated	812	918
Finance receivables evaluated collectively	19,699	25,236
Finance receivables	20,511	26,154	48,704
Impaired receivables in nonaccrual status	156	178
Amount of the specific reserve for impaired accounts	378	492
Amount of the general component of the allowance	1,092	1,401
Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired receivables specifically evaluated	130	110
Finance receivables evaluated collectively	29,190	30,319
Finance receivables	29,320	30,429	$ 31,851
Impaired receivables in nonaccrual status	36	37
Amount of the specific reserve for impaired accounts	65	61
Amount of the general component of the allowance	$ 1,855	$ 1,885

The amount of allowance for credit losses excluding the specific reserve associated with impaired accounts.

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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

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- Definition

Amount of allowance for credit losses related to recorded investment.

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-Publisher FASB
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-SubTopic 10
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- Definition

Reflects the carrying amount of loans deemed to be questionable as to collection on which no interest is continuing to be recognized.

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-Publisher FASB
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- Definition

Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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