Organization and operations (Details)			0 Months Ended
	Jun. 30, 2014 property state	Dec. 31, 2013 property	Jun. 10, 2013 Operating Partnership Series D Convertible Units	Jun. 10, 2013 Operating Partnership Series E Convertible Units
Organization and operations
Number of properties	27,173	23,268
Number of states	22
Number of properties held for sale	36
Organization and operations
Issuance of units (in shares)			4,375,000	4,375,000