Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Senior Notes [Member]	Line of Credit	Secured Debt [Member]	Series A Cumulative Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in-Capital	Retained Earnings (Distributions in excess of net earnings)	Accumulated Other Comprehensive Income	Operating Partnership	Consolidated Joint Venture	Preferred Capital in Consolidated Joint Venture [Member]
Balance (in shares) at Dec. 31, 2018					12,879,475	174,019,616
Balance at Dec. 31, 2018	$ 3,496,941				$ 366,936	$ 1,740	$ 3,195,381	$ (150,476)	$ 16,195	$ 10,827	$ 11,908	$ 44,430
Increase (Decrease) in Owners' Equity
Net income (loss)	62,013									233	(256)	1,339
Unrealized loss on interest rate derivatives	(35,781)								(35,781)
Reclassification of unrealized gain on discontinued cash flow hedges to interest expense	(2,250)								(2,250)
Redemption of Operating Partnership units	(9)									(9)
Contributions from consolidated joint venture partners	2,305										2,305
Share grants to trustees (in shares)						530,436
Share grants to trustees	0					$ 5	(5)
Amortization of share-based compensation	6,032						6,032
Shares acquired to satisfy minimum required federal and state tax withholding on vesting restricted stock (in shares)						(34,880)
APIC, Share-based Payment Arrangement, Restricted Stock Unit, Increase for Cost Recognition	$ 656						656
Shares acquired as part of a share repurchase program (in shares)	(1,049,215)					(1,049,215)
Shares acquired as part of a share repurchase program	$ (18,411)					$ (10)	(18,401)
Forfeiture of restricted stock (in shares)						(6,942)
Restricted Stock Award, Forfeitures	0
Dividends, Preferred Stock	(12,557)							(12,557)
Distributions on common shares and units	(114,857)							(114,247)		(610)
Preferred distributions - consolidated joint venture	(186)											(186)
Redemption of preferred equity - consolidated joint venture	(45,583)											(45,583)
Balance (in shares) at Jun. 30, 2019					12,879,475	173,459,015
Balance at Jun. 30, 2019	3,337,001				$ 366,936	$ 1,735	3,182,351	(216,583)	(21,836)	10,441	13,957	0
Increase (Decrease) in Owners' Equity
Net Income (Loss) Attributable to Parent	60,697							60,697
Interest expense		$ 11,888	$ 20,991	$ 10,573
Amortization of deferred financing costs	1,902
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	(55)
Total Interest Expense	45,299
Balance (in shares) at Mar. 31, 2019					12,879,475	173,667,027
Balance at Mar. 31, 2019	3,393,222				$ 366,936	$ 1,737	3,187,285	(187,092)	(191)	10,686	13,861
Increase (Decrease) in Owners' Equity
Net income (loss)	33,681									141	96
Unrealized loss on interest rate derivatives	(21,645)								(21,645)
Reclassification of unrealized gain on discontinued cash flow hedges to interest expense	0
Share grants to trustees (in shares)						259,408
Share grants to trustees	0					$ 3	(3)
Amortization of share-based compensation	3,204						3,204
Shares acquired to satisfy minimum required federal and state tax withholding on vesting restricted stock (in shares)						(15,606)
APIC, Share-based Payment Arrangement, Restricted Stock Unit, Increase for Cost Recognition	(290)						(290)
Shares acquired as part of a share repurchase program (in shares)						(446,906)
Shares acquired as part of a share repurchase program	(7,850)					$ (5)	(7,845)
Forfeiture of restricted stock (in shares)						(4,908)
Restricted Stock Award, Forfeitures	0
Dividends, Preferred Stock	(6,279)							(6,279)
Distributions on common shares and units	(57,042)							(56,656)		(386)
Preferred distributions - consolidated joint venture	0
Balance (in shares) at Jun. 30, 2019					12,879,475	173,459,015
Balance at Jun. 30, 2019	3,337,001				$ 366,936	$ 1,735	3,182,351	(216,583)	(21,836)	10,441	13,957	$ 0
Increase (Decrease) in Owners' Equity
Net Income (Loss) Attributable to Parent	33,444							33,444
Interest expense		5,944	10,838	5,150
Amortization of deferred financing costs	1,110
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	2,195
Total Interest Expense	25,237
Balance (in shares) at Dec. 31, 2019					12,879,475	169,852,246
Balance at Dec. 31, 2019	3,226,483				$ 366,936	$ 1,699	3,127,982	(274,769)	(19,514)	10,084	14,065
Increase (Decrease) in Owners' Equity
Net income (loss)	(146,995)									(760)	(1,837)
Unrealized loss on interest rate derivatives	(63,059)								(63,059)
Reclassification of unrealized gain on discontinued cash flow hedges to interest expense	0
Redemption of Operating Partnership units	(8)									(8)
Contributions from consolidated joint venture partners	1,264										1,264
Issuance of restricted stock (in shares)						801,463
Issuance of restricted stock	0					$ 8	(8)
Amortization of share-based compensation	6,487						6,487
Shares acquired to satisfy minimum required federal and state tax withholding on vesting restricted stock (in shares)						(62,987)
APIC, Share-based Payment Arrangement, Restricted Stock Unit, Increase for Cost Recognition	(849)					$ (1)	(848)
Shares acquired as part of a share repurchase program (in shares)						(5,489,335)
Shares acquired as part of a share repurchase program	(62,605)					$ (55)	(62,550)
Forfeiture of restricted stock (in shares)						(8,434)
Restricted Stock Award, Forfeitures	0					$ 0	0
Dividends, Preferred Stock	(12,557)							(12,557)
Distributions on common shares and units	(2,690)							(2,518)		(172)
Preferred distributions - consolidated joint venture	0
Balance (in shares) at Jun. 30, 2020					12,879,475	165,092,953
Balance at Jun. 30, 2020	2,945,471				$ 366,936	$ 1,651	3,071,063	(434,242)	(82,573)	9,144	13,492
Increase (Decrease) in Owners' Equity
Net Income (Loss) Attributable to Parent	(144,398)
Interest expense		11,883	23,356	9,115
Amortization of deferred financing costs	2,067
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	1,186
Total Interest Expense	47,607
Balance (in shares) at Mar. 31, 2020					12,879,475	164,842,781
Balance at Mar. 31, 2020	3,071,834				$ 366,936	$ 1,648	3,067,693	(311,223)	(75,991)	9,749	13,022
Increase (Decrease) in Owners' Equity
Net income (loss)	(116,166)									(568)	(524)
Unrealized loss on interest rate derivatives	(6,582)								(6,582)
Reclassification of unrealized gain on discontinued cash flow hedges to interest expense	0
Contributions from consolidated joint venture partners	994										994
Issuance of restricted stock (in shares)						276,294
Issuance of restricted stock	0					$ 3	(3)
Amortization of share-based compensation	3,588						3,588
Shares acquired to satisfy minimum required federal and state tax withholding on vesting restricted stock (in shares)						(24,112)
APIC, Share-based Payment Arrangement, Restricted Stock Unit, Increase for Cost Recognition	(215)					$ 0	(215)
Forfeiture of restricted stock (in shares)						(2,010)
Restricted Stock Award, Forfeitures	0
Dividends, Preferred Stock	(6,279)							(6,279)
Distributions on common shares and units	(1,703)							(1,666)		(37)
Preferred distributions - consolidated joint venture	0
Balance (in shares) at Jun. 30, 2020					12,879,475	165,092,953
Balance at Jun. 30, 2020	2,945,471				$ 366,936	$ 1,651	$ 3,071,063	$ (434,242)	$ (82,573)	$ 9,144	$ 13,492
Increase (Decrease) in Owners' Equity
Net Income (Loss) Attributable to Parent	(115,074)
Interest expense		$ 5,940	$ 12,705	$ 4,475
Amortization of deferred financing costs	1,045
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	(371)
Total Interest Expense	$ 23,794