Consolidated Statement Of Changes In Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Preferred Stock [Member]	Additional paid-in capital [Member]	Treasury shares [Member]	Accumulated other comprehensive income (loss) [Member]	Distributions in excess of net income [Member]	Series E Preferred Shares [Member]	Series E Preferred Shares [Member] Common Stock [Member]	Series E Preferred Shares [Member] Preferred Stock [Member]	Series C Preferred Shares [Member]	Series C Preferred Shares [Member] Common Stock [Member]	Series C Preferred Shares [Member] Preferred Stock [Member]	Series G Preferred Stock [Member]	Series G Preferred Stock [Member] Preferred Stock [Member]	Series G Preferred Stock [Member] Additional paid-in capital [Member]	Series F Preferred Stock [Member]	Series F Preferred Stock [Member] Preferred Stock [Member]	Series F Preferred Stock [Member] Additional paid-in capital [Member]
Balance (in shares) at Dec. 31, 2015		63,195,182	13,850,000
Balance at Dec. 31, 2015	$ 2,073,868	$ 632	$ 139	$ 2,508,445	$ (97,328)	$ 5,622	$ (343,642)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted share units issued to Trustees (in shares)		15,805
Restricted share units issued to Trustees	0			0
Issuance of nonvested shares, net		300,752
Issuance of nonvested shares, net	4,475	$ 3		4,472	0
Treasury Stock, Retired, Cost Method, Amount	(4,211)				(4,211)
Amortization of nonvested shares	(10,255)			(10,255)
Adjustments to Additional Paid in Capital, Share-based Compensation, Nonvested Shares, Requisite Service Period Recognition	909			909
Foreign currency translation adjustment	5,142					5,142
Change in unrealized gain/loss on derivatives	(3,030)					(3,030)
Net income	224,982						224,982
Issuances of common shares (in shares)		2,521,071
Issuances of common shares, net of costs	142,848	$ 26		142,822
Stock Issued During Period, Value, Acquisitions	0
Stock Issued During Period, Shares, Conversion of Convertible Securities		358
Stock Redeemed or Called During Period, Shares													(950)
Preferred Share Redemption Costs	0
Payments for Repurchase of Redeemable Preferred Stock	0
Stock Redeemed or Called During Period, Value	0												$ 0
Proceeds from Issuance of Preferred Stock and Preference Stock	$ 0
Stock option exercises, net (in shares)	230,319	230,319
Stock option exercises, net	$ (1,488)	$ 2		10,143	11,633
Dividends to common and preferred shareholders	(267,849)						(267,849)
Balance (in shares) at Dec. 31, 2016		66,263,487	13,849,050
Balance at Dec. 31, 2016	2,185,901	$ 663	$ 139	2,677,046	(113,172)	7,734	(386,509)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted share units issued to Trustees (in shares)		19,030
Restricted share units issued to Trustees	0			0
Issuance of nonvested shares, net		296,914
Issuance of nonvested shares, net	5,498	$ 3		5,585	(90)
Treasury Stock, Retired, Cost Method, Amount	(6,729)				(6,729)
Amortization of nonvested shares	(13,446)			(13,446)
Adjustments to Additional Paid in Capital, Share-based Compensation, Nonvested Shares, Requisite Service Period Recognition	696			696
Foreign currency translation adjustment	12,569					12,569
Change in unrealized gain/loss on derivatives	(7,820)					(7,820)
Net income	262,968						262,968
Issuances of common shares (in shares)		1,398,280
Issuances of common shares, net of costs	99,336	$ 14		99,322
Stock Issued During Period, Shares, Acquisitions		8,851,264
Stock Issued During Period, Value, Acquisitions	657,473	$ 89		657,384
Stock Issued During Period, Shares, Conversion of Convertible Securities		404
Stock Redeemed or Called During Period, Shares										(885)								5,000,000
Preferred Share Redemption Costs	4,457						(4,457)										$ 4,500
Payments for Repurchase of Redeemable Preferred Stock	(125,025)																	$ 50	$ 120,518
Proceeds from Issuance of Preferred Stock, Preference Stock, and Warrants	144,490															$ 144,430
Stock Redeemed or Called During Period, Value	(1)									$ (1)
Proceeds from Issuance of Preferred Stock and Preference Stock	$ 144,490													$ 144,500	$ 60
Stock option exercises, net (in shares)	29,253	29,253
Stock option exercises, net	$ (5)	$ 0		1,595	1,600
Dividends to common and preferred shareholders	(315,472)						(315,472)
Balance (in shares) at Dec. 31, 2017		76,858,632	14,848,165
Balance at Dec. 31, 2017	2,927,325	$ 769	$ 148	3,478,986	(121,591)	12,483	(443,470)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Preferred Stock, Shares Issued								3,449,115			5,399,050			6,000,000	6,000,000
Restricted share units issued to Trustees (in shares)		23,571
Restricted share units issued to Trustees	0			0
Issuance of nonvested shares, net		295,202
Issuance of nonvested shares, net	3,974	$ 3		4,588	(617)
Treasury Stock, Retired, Cost Method, Amount	(7,156)				(7,156)
Amortization of nonvested shares	(14,826)			(14,826)
Adjustments to Additional Paid in Capital, Share-based Compensation, Nonvested Shares, Requisite Service Period Recognition	285			285
share based compensation included in severance expense	3,218			3,218
Foreign currency translation adjustment	(16,177)					(16,177)
Change in unrealized gain/loss on derivatives	15,779					15,779
Net income	266,983						266,983
Issuances of common shares (in shares)		20,553
Issuances of common shares, net of costs	1,286	$ 0		1,286
Stock Issued During Period, Value, Acquisitions	0
Stock Issued During Period, Shares, Conversion of Convertible Securities									800			1,964
Stock Redeemed or Called During Period, Shares										(1,734)			(5,000)
Preferred Share Redemption Costs	0
Payments for Repurchase of Redeemable Preferred Stock	0
Stock Redeemed or Called During Period, Value	0									$ 0			$ 0
Proceeds from Issuance of Preferred Stock and Preference Stock	$ 0
Stock option exercises, net (in shares)	25,721	25,721
Stock option exercises, net	$ (59)	$ 0		1,305	1,364
Dividends to common and preferred shareholders	(345,261)						(345,261)
Balance (in shares) at Dec. 31, 2018		77,226,443	14,841,431
Balance at Dec. 31, 2018	$ 2,865,023	$ 772	$ 148	$ 3,504,494	$ (130,728)	$ 12,085	$ (521,748)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Preferred Stock, Shares Issued								3,447,381			5,394,050			6,000,000