Percentage points added to the reference rate to compute the variable rate on the debt instrument.

No definition available.

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Namespace Prefix:	us-gaap_
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- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: 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(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Date the credit facility terminates, in CCYY-MM-DD format.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Balance Type:	na
Period Type:	duration

- 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.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	credit
Period Type:	instant

- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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Debt - Additional Information (Detail) - USD ($)	12 Months Ended
Debt - Additional Information (Detail) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Line of Credit Facility [Line Items]
Company indebtedness	$ 0	$ 0
Remaining available borrowing capacity	$ 200,000,000
Third Amended and Restated Credit Agreement [Member]
Line of Credit Facility [Line Items]
Termination date of the Credit Agreement	Jan. 12, 2021
Third Amended and Restated Credit Agreement [Member] \| Federal Funds Rate [Member]
Line of Credit Facility [Line Items]
Interest rate	0.50%
Third Amended and Restated Credit Agreement [Member] \| Eurodollar Rate Loans [Member]
Line of Credit Facility [Line Items]
Interest rate	1.00%
Fourth Amended And Restated Credit Agreement [Member]
Line of Credit Facility [Line Items]
Termination date of the Credit Agreement	Nov. 05, 2024
Fourth Amended And Restated Credit Agreement [Member] \| Federal Funds Rate [Member]
Line of Credit Facility [Line Items]
Interest rate	0.50%
Fourth Amended And Restated Credit Agreement [Member] \| Eurodollar Rate Loans [Member]
Line of Credit Facility [Line Items]
Interest rate	1.00%
Revolver Loans Portion Effective January 1 through June 30 [Member] \| Third Amended and Restated Credit Agreement [Member]
Line of Credit Facility [Line Items]
Revolving loans in a collective maximum principal amount	$ 250,000,000
Revolver Loans Portion Effective January 1 through June 30 [Member] \| Fourth Amended And Restated Credit Agreement [Member]
Line of Credit Facility [Line Items]
Revolving loans in a collective maximum principal amount	250,000,000
Revolver Loans Portion Effective July 1 through December 31 [Member] \| Third Amended and Restated Credit Agreement [Member]
Line of Credit Facility [Line Items]
Revolving loans in a collective maximum principal amount	200,000,000
Revolver Loans Portion Effective July 1 through December 31 [Member] \| Fourth Amended And Restated Credit Agreement [Member]
Line of Credit Facility [Line Items]
Revolving loans in a collective maximum principal amount	200,000,000
Revolving Credit Facility [Member] \| Letter of Credit Facility Sublimit [Member]
Line of Credit Facility [Line Items]
Revolving loans in a collective maximum principal amount	15,000,000
Revolving Credit Facility [Member] \| Swing Advance Loan Sublimit [Member]
Line of Credit Facility [Line Items]
Revolving loans in a collective maximum principal amount	$ 5,000,000