Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Preferred D Units	Preferred Operating Partnership, Series A	Preferred Operating Partnership, Series B	Preferred Operating Partnership, Series C	Preferred Operating Partnership, Series D	Preferred Operating Partnership, Series D Preferred D Units	Operating Partnership	Other	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income	Accumulated Deficit	Redemption of Operating Partnership units for sale of property	Redemption of Operating Partnership units for sale of property Operating Partnership	Redemption of Operating Partnership units for common stock and cash	Redemption of Operating Partnership units for common stock and cash Operating Partnership	Redemption of Operating Partnership units for common stock and cash Common Stock	Redemption of Operating Partnership units for common stock and cash Additional Paid-in Capital
Beginning balance at Dec. 31, 2014	$ 1,911,983		$ 14,809	$ 41,903	$ 10,730	$ 13,710		$ 92,422	$ 984	$ 1,163	$ 1,995,484	$ (1,484)	$ (257,738)
Beginning balance (in shares) at Dec. 31, 2014										116,360,239
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon the exercise of options (in shares)	79,974									79,974
Issuance of common stock upon the exercise of options	$ 1,542									$ 1	1,541
Restricted stock grants issued (in shares)										174,558
Restricted stock grants issued	2									$ 2
Restricted stock grants cancelled (in shares)										(18,090)
Restricted stock grants cancelled	0
Issuance of common stock, net of offering costs (in shares)										6,735,000
Issuance of common stock, net of offering costs	446,877									$ 67	446,810
Compensation expense related to stock-based awards	6,055										6,055
Purchase of remaining equity interest in existing consolidated joint venture	(1,268)								(822)		(446)
Issuance of Operating Partnership units in conjunction with acquisitions	142,399							142,399
Redemption of Operating Partnership units	0							(28,106)		$ 8	28,098
Redemption of Operating Partnership units (in shares)										787,850
Repurchase of equity portion of 2013 exchangeable senior notes	(70,112)										(70,112)
Issuance of 2015 exchangeable senior notes - equity component	22,597										22,597
Net income (loss)	209,536		6,445	2,514	2,074	685		8,344					189,474
Other comprehensive income (loss)	(4,929)		(15)					(46)				(4,868)
Tax effect from vesting of restricted stock grants and stock option exercises	1,727										1,727
Distributions to Operating Partnership units held by noncontrolling interests	(24,503)		(7,050)	(2,515)	(2,074)	(685)		(12,179)
Dividends paid on common stock	(269,302)												(269,302)
Ending balance at Dec. 31, 2015	$ 2,372,604		14,189	41,902	10,730	13,710		202,834	162	$ 1,241	2,431,754	(6,352)	(337,566)
Ending balance (in shares) at Dec. 31, 2015										124,119,531
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon the exercise of options (in shares)	97,855									97,855
Issuance of common stock upon the exercise of options	$ 1,444										1,444
Restricted stock grants issued (in shares)										119,931
Restricted stock grants issued	2									$ 2
Restricted stock grants cancelled (in shares)										(9,947)
Restricted stock grants cancelled	0
Issuance of common stock, net of offering costs (in shares)										1,381,300
Issuance of common stock, net of offering costs	123,422									$ 14	123,408
Compensation expense related to stock-based awards	8,045										8,045
Purchase of remaining equity interest in existing consolidated joint venture	0							800	(162)		(638)
Issuance of Operating Partnership units in conjunction with acquisitions	7,247	$ 67,193					$ 67,193	7,247
Redemption of Operating Partnership units														$ (7,689)	$ (7,689)	$ (506)	$ (1,083)		$ 577
Redemption of Operating Partnership units (in shares)																		23,850
Repurchase of equity portion of 2013 exchangeable senior notes (in shares)										148,940
Repurchase of equity portion of 2013 exchangeable senior notes	(872)									$ 2	(874)
Net income (loss)	397,089		7,645	2,514	2,570	1,971		16,262					366,127
Other comprehensive income (loss)	24,598		201					1,275				23,122
Tax effect from vesting of restricted stock grants and stock option exercises	2,404										2,404
Distributions to Operating Partnership units held by noncontrolling interests	(30,997)		(7,650)	(2,514)	(2,570)	(1,971)		(16,292)
Dividends paid on common stock	(367,818)												(367,818)
Ending balance at Dec. 31, 2016	$ 2,596,166		14,385	41,902	10,730	80,903		203,354	0	$ 1,259	2,566,120	16,770	(339,257)
Ending balance (in shares) at Dec. 31, 2016	125,881,460									125,881,460
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon the exercise of options (in shares)	38,418									38,418
Issuance of common stock upon the exercise of options	$ 1,266										1,266
Restricted stock grants issued (in shares)										95,392
Restricted stock grants issued	0									$ 1	(1)
Restricted stock grants cancelled (in shares)										(8,179)
Restricted stock grants cancelled	0
Compensation expense related to stock-based awards	9,561										9,561
Purchase of remaining equity interest in existing consolidated joint venture	(2,510)							(1,238)			(1,272)
Issuance of Operating Partnership units in conjunction with acquisitions	7,618	$ 11,161					$ 11,161	7,618
Noncontrolling Interest in consolidated joint venture	216								216
Repurchase of equity portion of 2013 exchangeable senior notes	(6,189)										(6,189)
Net income (loss)	514,222		6,300	2,514	2,703	3,472		20,317	(97)				479,013
Other comprehensive income (loss)	17,308		106					682				16,520
Tax effect from vesting of restricted stock grants and stock option exercises	0
Distributions to Operating Partnership units held by noncontrolling interests	(31,972)		(5,851)	(2,514)	(2,703)	(3,472)		(17,432)
Dividends paid on common stock	(393,040)												(393,040)
Ending balance at Dec. 31, 2017	$ 2,723,807		$ 14,940	$ 41,902	$ 10,730	$ 92,064		$ 213,301	$ 119	$ 1,260	$ 2,569,485	$ 33,290	$ (253,284)
Ending balance (in shares) at Dec. 31, 2017	126,007,091									126,007,091,000