Organization and operations - Additional Information (Detail) (USD $)					1 Months Ended				6 Months Ended	1 Months Ended
	Jun. 30, 2013 State Property	Dec. 31, 2012 Property	Jun. 10, 2013 Operating Partnership [Member] Series D Convertible Units [Member]	Jun. 10, 2013 Operating Partnership [Member] Series E Convertible Units [Member]	Aug. 21, 2013 Subsequent Events [Member] Class A Common Shares [Member]	Dec. 31, 2012 2012 Offering [Member] Property	Dec. 31, 2012 2012 Offering [Member] Sponsor [Member]	Mar. 31, 2013 2013 Offering [Member]	Jun. 30, 2013 2013 Offering [Member]	Aug. 21, 2013 IPO [Member] Subsequent Events [Member]	Aug. 06, 2013 IPO [Member] Subsequent Events [Member]	Aug. 21, 2013 IPO [Member] Subsequent Events [Member] Class A Common Shares [Member]	Aug. 06, 2013 Private Placement [Member] Subsequent Events [Member]
Schedule Of Description Of Business [Line Items]
Number of properties	18,326	3,644				367
Number of states	21
Proceeds from offering before fees						$ 530,413,000	$ 5,307,000	$ 747,500,000		$ 105,882,000	$ 705,882,000		$ 75,000,000
Fees associated with the sale of stock						40,928,000		44,003,000	44,003,000	5,029,000
Underwriting discounts and offering costs											$ 36,952,000
Option to purchase additional shares in offering					55,422,794							6,617,647
Issuance of units			4,375,000	4,375,000