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Derivative Financial Instruments - Additional Information (Detail) - USD ($)	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2018	Apr. 17, 2017	Dec. 31, 2016	Jun. 24, 2016
Derivative Instruments Gain Loss [Line Items]
Derivative, notional amount	$ 350,000,000	$ 350,000,000			$ 350,000,000
Derivative, strike rate for the interest rate swap contract				1.1325%		1.145%
Realized gains (losses) on interest rate hedges reclassified to earnings	27,000	(156,000)
Interest Rate Swap
Derivative Instruments Gain Loss [Line Items]
Derivative, notional amount	150,000,000	$ 150,000,000				$ 150,000
Derivative, maturity date		Jun. 17, 2021
Recognition of hedge ineffectiveness	(12,000)	$ 0
Interest Rate Swap | Cash Flow Hedge
Derivative Instruments Gain Loss [Line Items]
Derivative, notional amount	$ 150,000,000	$ 150,000,000			$ 150,000,000
Interest Rate Swaps and Caps | Scenario, Forecast | Cash Flow Hedge
Derivative Instruments Gain Loss [Line Items]
Reclassified out of accumulated other comprehensive income to earnings, amount			$ 471,000

X

- Definition

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

+ Details

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- Definition

Interest rate cash flow hedge gain loss reclassified to earnings net of mark to market.

+ References

No definition available.

+ Details

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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 effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4D
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624177-113959

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- Definition

Date the derivative contract matures, in CCYY-MM-DD format.

+ References

No definition available.

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- Definition

Fixed interest rate that will be received or paid upon exercise of the interest rate swaption contract.

+ References

No definition available.

+ Details

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- Definition

The net gain (loss) during the reporting period due to ineffectiveness in interest rate cash flow hedges. Recognized in earnings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (d)(1)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

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