Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Redemption of Operating Partnership units for sale of property	Redemption of Operating Partnership units for common stock and cash	Redemption of Operating Partnership units for cash	Preferred Operating Partnership, Series A	Preferred Operating Partnership, Series B	Preferred Operating Partnership, Series C	Preferred Operating Partnership, Series D	Operating Partnership	Operating Partnership Redemption of Operating Partnership units for sale of property	Operating Partnership Redemption of Operating Partnership units for common stock and cash	Operating Partnership Redemption of Operating Partnership units for cash	Operating Partnership Redemption of Operating Partnership units for stock	Other	Common Stock	Common Stock Redemption of Operating Partnership units for common stock and cash	Common Stock Redemption of Operating Partnership units for stock	Additional Paid-in Capital	Additional Paid-in Capital Redemption of Operating Partnership units for common stock and cash	Additional Paid-in Capital Redemption of Operating Partnership units for cash	Accumulated Other Comprehensive Income	Accumulated Deficit
Beginning 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)
Beginning 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														$ 0			1,444
Restricted stock grants issued (in shares)															119,931
Restricted stock grants issued	2														$ 2
Restricted stock grants cancelled (in shares)															(9,947)
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
Issuance of Operating Partnership units in conjunction with acquisitions	7,247								7,247
Redemption or purchase of noncontrolling interests		$ (7,689)	$ (506)						800	$ (7,689)	$ (1,083)			(162)				(638)	$ 577
Redemption of Operating Partnership units (in shares)																23,850
Issuance of Preferred D Units in the Operating Partnership in conjunction with acquisitions	67,193							67,193										0
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	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
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															$ 1			(1)
Restricted stock grants cancelled (in shares)															(8,179)
Compensation expense related to stock-based awards	9,561																	9,561
Issuance of Operating Partnership units in conjunction with acquisitions	7,618								7,618
Redemption or purchase of noncontrolling interests				$ (2,510)								$ (1,238)								$ (1,272)
Issuance of Preferred D Units in the Operating Partnership in conjunction with acquisitions	11,161							11,161
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	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
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon the exercise of options (in shares)	54,575														54,575
Issuance of common stock upon the exercise of options	$ 1,169																	1,169
Restricted stock grants issued (in shares)															85,066
Restricted stock grants issued	1														$ 1			0
Restricted stock grants cancelled (in shares)															(11,771)
Issuance of common stock, net of offering costs (in shares)															933,789
Issuance of common stock, net of offering costs	90,231														$ 10			90,221
Compensation expense related to stock-based awards	11,176																	11,176
Repayment of receivable for preferred operating units pledged as collateral on loan	495						495
Issuance of Operating Partnership units in conjunction with acquisitions	1,877								1,877
Redemption or purchase of noncontrolling interests				$ (2,558)								$ (1,126)	$ (1,337)							$ (1,432)
Redemption of Operating Partnership units (in shares)																	35,000
Conversion of Preferred C Units in the Operating Partnership for Common Operating Partnership Units							(6,851)		6,851
Noncontrolling interest in consolidated joint venture	122													122
Repurchase of equity portion of 2013 exchangeable senior notes	(31,251)																	(31,251)
Net income (loss)	447,080				5,035	2,514	2,731	3,715	17,797					(1)								415,289
Other comprehensive income	1,430				12				58												1,360
Tax effect from vesting of restricted stock grants and stock option exercises	0
Distributions to Operating Partnership units held by noncontrolling interests	(33,250)				(5,231)	(2,514)	(2,731)	(3,715)	(19,059)
Dividends paid on common stock	(424,907)																					(424,907)
Ending balance at Dec. 31, 2018	$ 2,785,422				$ 14,756	$ 41,902	$ 4,374	$ 92,064	$ 218,362					$ 240	$ 1,271			$ 2,640,705			$ 34,650	$ (262,902)
Ending balance (in shares) at Dec. 31, 2018	127,103,750														127,103,750