Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in-Capital	Retained Earnings (Distributions in excess of net earnings)	Accumulated Other Comprehensive Loss	Operating Partnership	Consolidated Joint Venture	Retained Earnings [Member]	Series A Cumulative Preferred Stock [Member]	Preferred Capital in Consolidated Joint Venture [Member]
Net Income (Loss) Attributable to Parent	$ 200,352
Balance (in shares) at Dec. 31, 2015		124,635,675
Balance at Dec. 31, 2015	2,200,524	$ 1,246	$ 2,195,732	$ 2,439	$ (16,602)	$ 11,532	$ 6,177
Increase (Decrease) in Equity
Net income	201,314			200,352		907	55
Unrealized gain (loss) on interest rate derivatives	11,700				11,700
Redemption of Operating Partnership units, shares		335,250
Redemption of Operating Partnership units, value	$ 0	$ 3	4,322			(4,325)
Number of shares acquired as part of a share repurchase program (in shares)	(610,607)	(610,607)
Shares acquired as part of a share repurchase program	$ (13,271)	$ 6	13,265
Issuance of restricted stock (in shares)		672,821
Issuance of restricted stock	0	$ 7	(7)
Amortization of share-based compensation	5,990		5,990
Share grants to trustees (in shares)		2,554
Share grants to trustees	57		57
Shares acquired to satisfy minimum required federal and state tax withholding on vesting restricted stock (in shares)		244,015
Shares acquired to satisfy statutory minimum federal and state tax obligations on vesting restricted stock	(5,502)	$ (2)	(5,500)
Forfeiture of restricted stock (in shares)		(427,500)
Restricted Stock Award, Forfeitures	0	$ 4	(4)
Distribution to joint venture partner	(259)						259
Distributions on common shares and units	(165,276)			164,542		734
Balance (in shares) at Dec. 31, 2016		124,364,178							0
Balance at Dec. 31, 2016	2,235,277	$ 1,244	2,187,333	38,249	(4,902)	7,380	5,973		$ 0	$ 0
Increase (Decrease) in Equity
Preferred Stock Dividends and Other Adjustments	0
Net Income (Loss) Attributable to Parent	74,835
Net income	75,739					291	117			496
Unrealized gain (loss) on interest rate derivatives	$ 13,748				13,748
Redemption of Operating Partnership units, shares		335,250
Number of shares acquired as part of a share repurchase program (in shares)	(122,508)	(122,508)
Shares acquired as part of a share repurchase program	$ (2,610)	$ 1	2,609
Issuance of restricted stock (in shares)		425,076
Issuance of restricted stock	0	$ 4	(4)
Amortization of share-based compensation	10,607		10,607
Shares acquired to satisfy minimum required federal and state tax withholding on vesting restricted stock (in shares)		144,766
Shares acquired to satisfy statutory minimum federal and state tax obligations on vesting restricted stock	(3,050)	$ (2)	(3,048)
Forfeiture of restricted stock (in shares)		(11,038)
Restricted Stock Award, Forfeitures	0	$ 0	0
Contributions from a noncontrolling interest	117						117
Dividends, Preferred Stock	(8,372)							$ (8,372)
Distributions on common shares and units	(188,110)			187,278		832
Balance (in shares) at Dec. 31, 2017		174,869,046							12,879,475
Balance at Dec. 31, 2017	3,570,278	$ 1,749	3,208,002	(82,566)	8,846	11,181	11,700		$ 366,936	44,430
Increase (Decrease) in Equity
Preferred Stock Dividends and Other Adjustments	(496)									496
Net Income (Loss) Attributable to Parent	188,643
Net income	190,862					719	17			1,483
Unrealized gain (loss) on interest rate derivatives	7,349				7,349
Redemption of Operating Partnership units, shares		0
Redemption of Operating Partnership units, value	$ (14)	$ 0	0			(14)
Number of shares acquired as part of a share repurchase program (in shares)	(1,162,557)	(1,162,557)
Shares acquired as part of a share repurchase program	$ (21,814)	$ (12)	(21,802)
Issuance of restricted stock (in shares)		592,673
Issuance of restricted stock	0	$ 6	(6)
Amortization of share-based compensation	12,769		12,769
Shares acquired to satisfy minimum required federal and state tax withholding on vesting restricted stock (in shares)		(166,221)
Shares acquired to satisfy statutory minimum federal and state tax obligations on vesting restricted stock	(3,585)	$ (2)	(3,583)
Forfeiture of restricted stock (in shares)		(113,325)
Restricted Stock Award, Forfeitures	0	$ (1)	1
Contributions from a noncontrolling interest	191						191
Dividends, Preferred Stock	(25,115)							$ (25,115)
Distributions on common shares and units	(232,497)			(231,438)		(1,059)
Balance (in shares) at Dec. 31, 2018		174,019,616							12,879,475
Balance at Dec. 31, 2018	3,496,941	$ 1,740	$ 3,195,381	$ (150,476)	$ 16,195	$ 10,827	$ 11,908		$ 366,936	44,430
Increase (Decrease) in Equity
Preferred Stock Dividends and Other Adjustments	$ (1,483)									$ (1,483)