CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - 3 months ended Mar. 31, 2018 - USD ($) $ in Thousands	Total	Series D	Cumulative Preferred Distributions	Common Shares	Cumulative Common Distributions	Additional Paid in Capital	Cumulative Net Income	Cumulative Other Comprehensive Loss	Noncontrolling Interest
Balance (in shares) at Dec. 31, 2017	124,217,616	4,915,196		124,217,616
Balance at Dec. 31, 2017	$ 3,300,495	$ 119,263	$ (685,748)	$ 1,242	$ (3,111,868)	$ 4,380,313	$ 2,596,259	$ (95)	$ 1,129
Increase (Decrease) in Stockholders' Equity
Net income	187,662						187,599		63
Unrealized gain on derivative instruments	117							117
Unrealized loss on marketable securities	(226)							(226)
Repurchase of shares (in shares)				(3,027,557)
Repurchase of shares	(89,910)			$ (30)		(89,880)
Share-based compensation (in shares)				267,014
Share-based compensation	5,338			$ 2		5,010			326
Contributions	0								0
Distributions	$ (1,997)		(1,997)
Adjustment for noncontrolling interest						329			(329)
Balance (in shares) at Mar. 31, 2018	121,457,073	4,915,196		121,457,073
Balance at Mar. 31, 2018	$ 3,401,479	$ 119,263	$ (687,745)	$ 1,214	$ (3,111,868)	$ 4,295,772	$ 2,785,760	$ (2,106)	$ 1,189