CONSOLIDATED STATEMENTS OF EQUITY - USD ($) shares in Thousands, $ in Thousands	Total Shareholders' Equity	Common Shares	Preferred Shares	Additional Paid-in Capital	Accumulated Other Comprehensive (Loss) Income	Accumulated Deficit	Noncontrolling Interest in Subsidiaries	Noncontrolling Interests in Operating Partnership	Total
Balance at Dec. 31, 2014	$ 1,448,026	$ 1,639	$ 31	$ 1,974,308	$ (8,759)	$ (519,193)	$ 1,592		$ 1,449,618
Balance (in shares) at Dec. 31, 2014		163,957	3,100
Balance of Noncontrolling Interests in the Operating Partnership at Dec. 31, 2014								$ 49,823
Increase (Decrease) in Stockholders' Equity
Contributions from noncontrolling interests in subsidiaries							178		178
Issuance of common shares, net	136,662	$ 56		136,606					136,662
Issuance of common shares, net (in shares)		5,515
Issuance of restricted shares	1	$ 1							1
Issuance of restricted shares (in shares)		161
Issuance of OP Units								500
Conversion from units to shares	1,705	$ 1		1,704				(1,705)	1,705
Conversion from units to shares (in shares)		66
Exercise of stock options	13,396	$ 12		13,384					13,396
Exercise of stock options (in shares)		1,228
Amortization of restricted shares	509			509					509
Share compensation expense	741			741					741
Adjustment for noncontrolling interest in the Operating Partnership	(12,166)					(12,166)		12,166	(12,166)
Net income (loss)	40,596					40,596	(56)		40,540
Net income (loss)								475
Other comprehensive income (loss), net	(65)				(65)		(11)		(76)
Other comprehensive income (loss), net								(2)
Preferred share distributions	(4,506)					(4,506)			(4,506)
Common share distributions	(80,817)					(80,817)		(1,077)	(80,817)
Balance at Sep. 30, 2015	1,544,082	$ 1,709	$ 31	2,127,252	(8,824)	(576,086)	1,703		1,545,785
Balance (in shares) at Sep. 30, 2015		170,927	3,100
Balance of Noncontrolling Interests in the Operating Partnership at Sep. 30, 2015								60,180
Balance at Dec. 31, 2014	1,448,026	$ 1,639	$ 31	1,974,308	(8,759)	(519,193)	1,592		1,449,618
Balance (in shares) at Dec. 31, 2014		163,957	3,100
Balance of Noncontrolling Interests in the Operating Partnership at Dec. 31, 2014								49,823
Balance at Dec. 31, 2015	1,643,327	$ 1,747	$ 31	2,231,181	(4,978)	(584,654)	1,526		1,644,853
Balance (in shares) at Dec. 31, 2015		174,668	3,100
Balance of Noncontrolling Interests in the Operating Partnership at Dec. 31, 2015								66,128	66,128
Increase (Decrease) in Stockholders' Equity
Contributions from noncontrolling interests in subsidiaries							4,447		4,447
Issuance of common shares, net	136,150	$ 44		136,106					136,150
Issuance of common shares, net (in shares)		4,408
Issuance of restricted shares	1	$ 1							1
Issuance of restricted shares (in shares)		123
Issuance of OP Units								1,500
Exercise of stock options	12,573	$ 7		12,566					12,573
Exercise of stock options (in shares)		660
Amortization of restricted shares	1,041			1,041					1,041
Share compensation expense	942			942					942
Adjustment for noncontrolling interest in the Operating Partnership	6,404					6,404		(6,404)	6,404
Net income (loss)	61,058					61,058	(411)		60,647
Net income (loss)								682
Other comprehensive income (loss), net	1,731				1,731				1,731
Other comprehensive income (loss), net								21
Preferred share distributions	(4,506)					(4,506)			(4,506)
Common share distributions	(112,550)					(112,550)		(1,386)	(112,550)
Balance at Sep. 30, 2016	$ 1,746,171	$ 1,799	$ 31	$ 2,381,836	$ (3,247)	$ (634,248)	$ 5,562		1,751,733
Balance (in shares) at Sep. 30, 2016		179,859	3,100
Balance of Noncontrolling Interests in the Operating Partnership at Sep. 30, 2016								$ 60,541	$ 60,541