CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Cumulative Preferred Distributions	Common Shares	Cumulative Common Distributions	Additional Paid in Capital	Cumulative Net Income	Cumulative Other Comprehensive Income (Loss)	Noncontrolling Interest	Series D	Series E
Balance (in shares) at Dec. 31, 2015			126,349,914						4,915,196	11,000,000
Balance at Dec. 31, 2015	$ 3,368,487	$ (650,195)	$ 1,263	$ (3,111,868)	$ 4,414,611	$ 2,333,709	$ (3,687)	$ 0	$ 119,263	$ 265,391
Increase (Decrease) in Stockholders' Equity
Net (loss) income	134,246					134,246		0
Unrealized gain (loss) on derivative instrument	1,453						1,453
Unrealized gain on marketable securities	0
Purchase of shares (in shares)			(983,789)
Purchase of shares	(25,563)		$ (10)		(25,553)
Redemption of shares (in shares)										(11,000,000)
Redemption of shares	(275,000)									$ (275,000)
Excess fair value of consideration paid over carrying value of preferred shares	(9,609)	(9,609)								$ 9,609
Share-based compensation (in shares)			167,251
Share-based compensation	8,977		$ 2		8,975			0
Distributions	(13,962)	(13,962)
Balance (in shares) at Jun. 30, 2016			125,533,376						4,915,196	0
Balance at Jun. 30, 2016	$ 3,198,638	(673,766)	$ 1,255	(3,111,868)	4,398,033	2,467,955	(2,234)	0	$ 119,263	$ 0
Balance (in shares) at Dec. 31, 2016	123,994,465		123,994,465						4,915,196	0
Balance at Dec. 31, 2016	$ 3,260,447	(677,760)	$ 1,240	(3,111,868)	4,363,177	2,566,603	(208)	0	$ 119,263	$ 0
Increase (Decrease) in Stockholders' Equity
Net (loss) income	18,011					18,005		6
Unrealized gain (loss) on derivative instrument	(261)						(261)
Unrealized gain on marketable securities	1,704						1,704
Purchase of shares (in shares)			(6,694)
Purchase of shares	(209)		$ 0		(209)
Excess fair value of consideration paid over carrying value of preferred shares	0
Share-based compensation (in shares)			101,672
Share-based compensation	10,732		$ 1		10,192			539
Contributions	31							31
Distributions	$ (3,994)	(3,994)
Adjustment for noncontrolling interest					(550)			550
Balance (in shares) at Jun. 30, 2017	124,089,443		124,089,443						4,915,196	0
Balance at Jun. 30, 2017	$ 3,286,461	$ (681,754)	$ 1,241	$ (3,111,868)	$ 4,372,610	$ 2,584,608	$ 1,235	$ 1,126	$ 119,263	$ 0