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Derivative Financial Instruments - Additional Information (Detail) - USD ($)				1 Months Ended	12 Months Ended
	Nov. 17, 2017	Jun. 24, 2016	Sep. 30, 2015	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jan. 04, 2018	Nov. 20, 2017	Apr. 17, 2017
Derivative Instruments Gain Loss [Line Items]
Derivative, notional amount				$ 250,000,000		$ 250,000,000	$ 350,000,000
Derivative, strike rate for the interest rate swap contract		1.145%									1.1325%
Realized gains (losses) on interest rate hedges reclassified to earnings						(107,000)	(492,000)	$ 0
Unsecured Term Loan
Derivative Instruments Gain Loss [Line Items]
Secured credit facility borrowing capacity	$ 100,000,000									$ 100,000,000
Cash Flow Hedge
Derivative Instruments Gain Loss [Line Items]
Derivative, notional amount				200,000,000		200,000,000	150,000,000
Cash Flow Hedge | 1-month LIBOR
Derivative Instruments Gain Loss [Line Items]
Interest rate cap strike rate			3.00%
Freestanding Derivatives | Other Income (Expense)
Derivative Instruments Gain Loss [Line Items]
Recognized gain on derivatives				94,000
Interest Rate Swap
Derivative Instruments Gain Loss [Line Items]
Derivative, notional amount		$ 150,000,000
Derivative, maturity date		Jun. 17, 2021
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 Collar | Cash Flow Hedge
Derivative Instruments Gain Loss [Line Items]
Derivative, notional amount	$ 100,000,000			50,000,000		50,000,000
Derivative, maturity date	Nov. 17, 2024
Interest rate cap strike rate	2.00%
Floor interest rate	1.25%
Interest Rate Collar | Cash Flow Hedge | Designated
Derivative Instruments Gain Loss [Line Items]
Derivative, notional amount	$ 50,000,000
Interest Rate Collar | Freestanding Derivatives
Derivative Instruments Gain Loss [Line Items]
Derivative, notional amount	$ 50,000,000			$ 50,000,000		$ 50,000,000
Interest Rate Collar | Freestanding Derivatives | Designated | Subsequent Event
Derivative Instruments Gain Loss [Line Items]
Derivative, notional amount									$ 50,000,000
Interest Rate Cap | Cash Flow Hedge
Derivative Instruments Gain Loss [Line Items]
Derivative, notional amount			$ 200,000,000
Derivative, maturity date			Oct. 17, 2017
Interest Rate Cap | Freestanding Derivatives
Derivative Instruments Gain Loss [Line Items]
Derivative, notional amount							$ 200,000,000
Interest Rate Swaps and Caps | Cash Flow Hedge | Scenario, Forecast
Derivative Instruments Gain Loss [Line Items]
Reclassified out of accumulated other comprehensive income to earnings, amount					$ 954,000

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

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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

Cap rate on an interest rate derivative such as an interest rate cap or collar. If market rates exceed the cap rate, a payment or receipt is triggered on the contract.

+ References

No definition available.

+ Details

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- Definition

Floor rate on an interest rate derivative such as an interest rate floor or collar. If market rates falls below the floor rate, a payment or receipt is triggered on the contract.

+ References

No definition available.

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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.

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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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- 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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-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

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