Subsequent events - Additional Information (Detail) (USD $)		1 Months Ended				1 Months Ended
	Jun. 30, 2013 Property	Aug. 31, 2013 Subsequent Events [Member]	Aug. 06, 2013 Subsequent Events [Member]	Aug. 22, 2013 Subsequent Events [Member]	Jul. 31, 2013 Subsequent Events [Member] Property	Aug. 21, 2013 Subsequent Events [Member] Class A Common Shares [Member]	Aug. 21, 2013 Subsequent Events [Member] IPO [Member]	Aug. 06, 2013 Subsequent Events [Member] IPO [Member]	Aug. 21, 2013 Subsequent Events [Member] IPO [Member] Class A Common Shares [Member]	Aug. 06, 2013 Subsequent Events [Member] Private Placement [Member]
Subsequent Event [Line Items]
Number of properties acquired	1,872				1,499
Aggregate purchase price of properties acquired	$ 272,091,000				$ 208,762,000
Proceeds from offering before fees							105,882,000	705,882,000		75,000,000
Underwriting discounts and offering costs								36,952,000
Price per share								$ 16.00		$ 16.00
Fees associated with the sale of stock							5,029,000
Option to purchase additional shares in offering						55,422,794			6,617,647
Credit facility, additional borrowings, amount			170,000,000
Credit facility, amount outstanding			840,000,000	34,000,000
Credit facility, repayment, amount		90,000,000	716,000,000
Credit facility, maximum borrowing capacity			$ 500,000,000