Noncontrolling Interest Represented by Preferred Operating Partnership Units - Series B Redeemable Preferred Units - Additional Information (Detail) $ / shares in Units, $ in Thousands				6 Months Ended
	Apr. 03, 2014 USD ($) Store shares	Sep. 26, 2013 USD ($) Store shares	Aug. 29, 2013 Store	Jun. 30, 2015 USD ($) $ / shares	Jun. 30, 2014 USD ($)
Noncontrolling Interest in Operating Partnership [Line Items]
Debt assumed					$ 33,190
Series B Redeemable Preferred Units [Member] | Series B Units [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Liquidation value (in dollars per share) | $ / shares				$ 25.00
Fixed liquidation value				$ 41,903
Annual rate of return (as a percent)				6.00%
Series B Redeemable Preferred Units [Member] | Georgia, 1 Property Acquired 4/3/2014 [Member] | Series B Units [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Preferred units issued as part of acquisition (in units) | shares	333,360
Preferred units issued as part of acquisition	$ 8,334
Series B Redeemable Preferred Units [Member] | Georgia, 1 Property Acquired 4/3/2014 [Member] | Operating Partnership [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Cash portion of payment for acquisition	$ 15,158
Number of stores acquired | Store	1
Series B Redeemable Preferred Units [Member] | California, 20 Properties Acquired 2013-September [Member] | Operating Partnership [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Cash portion of payment for acquisition		$ 100,876
Number of stores acquired | Store		1	19
Number of stores acquired as part of portfolio acquisition | Store			20
Debt assumed		$ 98,960
Number of common units issued as part of acquisition | shares		1,448,108
OP units issued as part of the acquisition		$ 62,341
Series B Redeemable Preferred Units [Member] | California, 20 Properties Acquired 2013-September [Member] | Operating Partnership [Member] | Series B Units [Member]
Noncontrolling Interest in Operating Partnership [Line Items]
Preferred units issued as part of acquisition (in units) | shares		1,342,727
Preferred units issued as part of acquisition		$ 33,568