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	56,477	$ 24		56,453					56,477
Issuance of common shares, net (in shares)		2,339
Issuance of restricted shares	1	$ 1							1
Issuance of restricted shares (in shares)		154
Issuance of OP Units								500
Conversion from units to shares	296			296				(296)	296
Conversion from units to shares (in shares)		12
Exercise of stock options	9,359	$ 10		9,349					9,359
Exercise of stock options (in shares)		976
Amortization of restricted shares	(36)			(36)					(36)
Share compensation expense	491			491					491
Adjustment for noncontrolling interest in the Operating Partnership	(2,913)					(2,913)		2,913	(2,913)
Net income (loss)	22,158					22,158	(15)		22,143
Net income (loss)								252
Other comprehensive income (loss), net	381				381		(3)		378
Other comprehensive income (loss), net								4
Preferred share distributions	(3,004)					(3,004)			(3,004)
Common share distributions	(53,433)					(53,433)		(724)	(53,433)
Balance at Jun. 30, 2015	1,477,803	$ 1,674	$ 31	2,040,861	(8,378)	(556,385)	1,752		1,479,555
Balance (in shares) at Jun. 30, 2015		167,438	3,100
Balance of Noncontrolling Interests in the Operating Partnership at Jun. 30, 2015								52,472
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							4,396		4,396
Issuance of common shares, net	88,602	$ 28		88,574					88,602
Issuance of common shares, net (in shares)		2,820
Issuance of restricted shares	1	$ 1							1
Issuance of restricted shares (in shares)		121
Issuance of OP Units								1,500
Exercise of stock options	12,199	$ 6		12,193					12,199
Exercise of stock options (in shares)		641
Amortization of restricted shares	171			171					171
Share compensation expense	623			623					623
Adjustment for noncontrolling interest in the Operating Partnership	(1,469)					(1,469)		1,469	(1,469)
Net income (loss)	36,174					36,174	(335)		35,839
Net income (loss)								399
Other comprehensive income (loss), net	355				355				355
Other comprehensive income (loss), net								4
Preferred share distributions	(3,004)					(3,004)			(3,004)
Common share distributions	(74,736)					(74,736)		(919)	(74,736)
Balance at Jun. 30, 2016	$ 1,702,243	$ 1,782	$ 31	$ 2,332,742	$ (4,623)	$ (627,689)	$ 5,587		1,707,830
Balance (in shares) at Jun. 30, 2016		178,250	3,100
Balance of Noncontrolling Interests in the Operating Partnership at Jun. 30, 2016								$ 68,581	$ 68,581