Consolidated Statement of Equity - 9 months ended Sep. 30, 2017 - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	AOCI Including Portion Attributable to Noncontrolling Interest	Parent	Operating Partnership Noncontrolling Interest	Partially Owned Properties Noncontrolling Interest	Noncontrolling Interest	Operating Partnership	Operating Partnership Partially Owned Properties Noncontrolling Interest
Balance at Dec. 31, 2016	$ 1,782,318	$ 1,360	$ 1,920,644	$ (197,261)	$ 13,708	$ 1,738,451	$ 43,142	$ 725	$ 43,867
Stockholders' Equity Attributable to Parent [Abstract]
Net proceeds from sale of common shares	804,453	430	804,023			804,453
Restricted share award grants, net	1,920	2	2,391	(473)		1,920
Purchase of OP Units	(3,757)						(3,757)		(3,757)
Conversion of OP Units			783			783	(783)		(783)
Dividends/distributions declared	(115,799)			(112,164)		(112,164)	(3,635)		(3,635)
Preferred distributions	(505)			(505)		(505)
Issuance of OP Units in connection with acquisitions	44,259						44,259		44,259
Contributions	47							47	47	$ 47	$ 47
Distributions	(266)							(266)	(266)	(266)	(266)
Buyout of Noncontrolling Interests - partially owned properties	(2,105)		(2,800)			(2,800)	719	(24)	695	(2,105)	(24)
Change in fair value of interest rate cap agreements	(1,696)				(1,696)	(1,696)				(1,696)
Net income	29,352			28,384		28,384	823	145	968	$ 29,352	$ 145
Adjustment for Noncontrolling Interests ownership in Operating Partnership			7,080			7,080	(7,080)		(7,080)
Balance at Sep. 30, 2017	$ 2,538,221	$ 1,792	$ 2,732,121	$ (282,019)	$ 12,012	$ 2,463,906	$ 73,688	$ 627	$ 74,315