Finance Receivables, Credit Quality Information, and Allowance for Credit Losses - Tabular Disclosure of Impaired Financing Receivables (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired receivables specifically evaluated	$ 20,381	$ 17,230
Finance receivables evaluated collectively	826,857	800,233
Finance receivables	847,238	817,463	$ 726,767
Impaired receivables in nonaccrual status	1,686	1,798
Amount of the specific reserve for impaired accounts	5,132	3,766
Amount of the general component of the allowance	43,318	45,144
Small Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired receivables specifically evaluated	6,291	5,094
Finance receivables evaluated collectively	378,399	370,678
Finance receivables	384,690	375,772	348,742
Impaired receivables in nonaccrual status	541	707
Amount of the specific reserve for impaired accounts	1,729	1,190
Amount of the general component of the allowance	22,240	23,559
Large Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired receivables specifically evaluated	12,553	10,303
Finance receivables evaluated collectively	379,548	336,915
Finance receivables	392,101	347,218	267,921
Impaired receivables in nonaccrual status	973	931
Amount of the specific reserve for impaired accounts	3,101	2,183
Amount of the general component of the allowance	16,597	15,365
Automobile Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired receivables specifically evaluated	1,422	1,724
Finance receivables evaluated collectively	37,992	59,699
Finance receivables	39,414	61,423	79,861
Impaired receivables in nonaccrual status	143	129
Amount of the specific reserve for impaired accounts	280	373
Amount of the general component of the allowance	2,362	3,652
Retail Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired receivables specifically evaluated	115	109
Finance receivables evaluated collectively	30,918	32,941
Finance receivables	31,033	33,050	$ 30,243
Impaired receivables in nonaccrual status	29	31
Amount of the specific reserve for impaired accounts	22	20
Amount of the general component of the allowance	$ 2,119	$ 2,568

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

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-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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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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- 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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