Financing Activity - Additional Information (Detail) - Subsequent Event Type [Domain] - Name of Property [Domain] - Variable Rate [Domain]		3 Months Ended			6 Months Ended
	Jan. 08, 2014 USD ($)	Jun. 30, 2015 USD ($) Extension	Mar. 31, 2015	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) Extension	Jun. 30, 2014 USD ($)	Aug. 03, 2015 USD ($)	Dec. 31, 2014 USD ($)	Apr. 17, 2013 USD ($)
Debt Instrument [Line Items]
Long-term Debt		$ 400,000,000			$ 400,000,000			$ 130,000,000
Amount outstanding		$ 120,000,000			$ 120,000,000
Revolving Credit Facility Extension Options Available | Extension		2			2
Repayments of Long-term Debt					$ (120,000,000)	$ (130,000,000)
Two Thousand Fourteen Term Loans [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 250,000,000
Sales Per Square Foot		$ 500
Percentage Of Debt Yield		11.00%	12.00%		11.00%
Debt Instrument, Number of Loan Entered During Period	2
Two Thousand Fourteen Term Loans [Member] | Minimum [Member]
Debt Instrument [Line Items]
Capitalization Rate		6.50%
Two Thousand Fourteen Term Loans [Member] | Maximum [Member]
Debt Instrument [Line Items]
Capitalization Rate		7.50%
2013 Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Senior Unsecured Credit Facility									$ 400,000,000.0
Amount outstanding		$ 120,000,000			$ 120,000,000		$ 100,000,000
Unused portion of line of credit		272,100,000			272,100,000		292,100,000
Interest expense excluding non-cash amortization of finance costs		1,300,000		$ 300,000	1,700,000	800,000
Non-cash amortization of deferred financing fees		$ 600,000		400,000	$ 1,000,000	700,000
Debt Instrument, Maturity Date					Jun. 26, 2018
Outstanding commitments					0.25%
Stated Interest Rate		1.30%			1.30%
Sales Per Square Foot					$ 500
Line of Credit Facility, Accordion Option, Minimum Incremental Increase		$ 5,000,000			5,000,000
Line of Credit Facility, Accordion Option, Minimum Increase		25,000,000			25,000,000
Repayments of Long-term Debt		150,000,000
Letters of Credit Outstanding, Amount		7,900,000			$ 7,900,000		$ 7,900,000
2013 Revolving Credit Facility [Member] | Minimum [Member]
Debt Instrument [Line Items]
Capitalization Rate					6.50%
2013 Revolving Credit Facility [Member] | Minimum [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Weighted average interest rate of Term Loan					1.20%
2013 Revolving Credit Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Capitalization Rate					7.50%
2013 Revolving Credit Facility [Member] | Maximum [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Weighted average interest rate of Term Loan					1.55%
2013 Revolving Credit Facility [Member] | First Extension [Member]
Debt Instrument [Line Items]
Outstanding commitments			0.15%
2013 Revolving Credit Facility [Member] | Second Extension [Member]
Debt Instrument [Line Items]
Outstanding commitments			0.20%
Term Loans [Member]
Debt Instrument [Line Items]
Interest expense excluding non-cash amortization of finance costs		2,000,000		$ 1,200,000	$ 3,200,000	2,200,000
Non-cash amortization of deferred financing fees		100,000			200,000	$ 100,000
Seven Year Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 100,000,000	$ 100,000,000			100,000,000
Debt Instrument, Interest Rate During Period		2.13%
Long-term Debt		$ 100,000,000			$ 100,000,000
Debt Instrument, Maturity Date					Jan. 31, 2021
Maximum amount available under revolving facility through accordion option		200,000,000			$ 200,000,000
Line of Credit Facility, Accordion Option, Minimum Incremental Increase		5,000,000			5,000,000
Line of Credit Facility, Accordion Option, Minimum Increase		25,000,000			25,000,000
Line of Credit Facility, Maximum Borrowing Capacity		$ 100,000,000.0			$ 100,000,000.0
Line of Credit Facility, Prepayment Penalty, Next Twelve Months	3.00%
Line of Credit Facility, Prepayment Penalty, Year Two	2.00%
Line of Credit Facility, Prepayment Penalty, Year Three	1.00%
Credit Agreements [Member]
Debt Instrument [Line Items]
Minimum tangible net worth		75.00%			75.00%
Net proceeds of equity issuances			75.00%
Maximum secured indebtedness			0.625
Funded Indebtedness Asset Value Ratio Minimum			0.60		0.60
Maximum Investments in Persons other than Subsidiaries, Consolidated Affiliates and Unconsolidated Affiliates					5.00%
Maximum Mortgages in Favor of the Borrower or any other Subsidiary			5.00%
Maximum Aggregate Value of Investments to Gross Asset Value			10.00%
Maximum Investments in Consolidation Exempt Entities to Gross Asset Value					25.00%
Maximum Projects Under Development to Gross Asset Value			15.00%
Aggregate of Consolidation Exempt Entities and Projects to Gross Asset Value			35.00%
Minimum ratio of Adjusted EBITDA to Fixed Charges		1.50			1.50
Percentage Of Debt Yield		11.00%			11.00%
Investment Percentage of Gross Asset Value					1.75
Maximum Ratio of Secured Indebtedness to Gross Asset Value			0.60
Percentage of distribution related to FFO		95.00%			95.00%
REIT Taxable Income distributions					110.00%
Minimum Percentage of Total Guarantors Required to be Guarantors Based on Gross Asset Value		95.00%			95.00%
2014 Five Year Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 150,000,000.0	$ 150,000,000			$ 150,000,000
Debt Instrument, Interest Rate During Period		1.63%
Long-term Debt		$ 150,000,000			$ 150,000,000
Debt Instrument, Maturity Date					Jan. 31, 2019
Maximum amount available under revolving facility through accordion option		300,000,000			$ 300,000,000
Line of Credit Facility, Accordion Option, Minimum Incremental Increase		5,000,000			5,000,000
Line of Credit Facility, Accordion Option, Minimum Increase		25,000,000			25,000,000
Line of Credit Facility, Maximum Borrowing Capacity		150,000,000.0			150,000,000.0
2015 Five Year Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 150,000,000			150,000,000
Debt Instrument, Interest Rate During Period		1.64%
Long-term Debt		$ 150,000,000			$ 150,000,000
Debt Instrument, Maturity Date					Jun. 30, 2020
Sales Per Square Foot		$ 500
2015 Five Year Term Loan [Member] | Minimum [Member]
Debt Instrument [Line Items]
Capitalization Rate		6.50%
2015 Five Year Term Loan [Member] | Maximum [Member]
Debt Instrument [Line Items]
Capitalization Rate		7.50%
Wells Fargo Bank , NA [Member] | 2013 Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Senior Unsecured Credit Facility		$ 400,000,000			$ 400,000,000
Maximum amount available under revolving facility through accordion option		$ 600,000,000			$ 600,000,000