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 C Preferred Shares [Member]	Series C Preferred Shares [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 E Preferred Shares [Member] Distributions in excess of net income [Member]	Series G Preferred Stock [Member]	Series G Preferred Stock [Member] Distributions in excess of net income [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total equity	$ 2,927,325	$ 769	$ 148	$ 3,478,986	$ (121,591)	$ 12,483	$ (443,470)
Balance (in shares) at Dec. 31, 2017		76,858,632	14,848,165
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of nonvested shares, net		295,202
Issuance of nonvested shares, net	(3,974)	$ (3)		(3,971)	0
Purchase of common shares for vesting	(7,116)				(7,116)
Share-based compensation expense	(3,791)			(3,791)
Foreign currency translation adjustment	(5,400)					(5,400)
Change in unrealized loss on derivatives	9,398					9,398
Net income	29,538						29,538
Issuances of common shares (in shares)		6,601
Issuances of common shares	382	$ 0		382
Dividends to common and preferred shareholders	(80,263)						(80,263)	$ (1,940)	$ (1,940)	$ (1,939)			$ (1,939)	$ (2,156)	$ (2,156)
Balance (in shares) at Mar. 31, 2018		77,161,235	14,846,431
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock Issued During Period, Shares, Conversion of Convertible Securities											800
Stock Redeemed or Called During Period, Shares												(1,734)
Stock Redeemed or Called During Period, Value	0											$ 0
Total equity	2,875,594	$ 772	$ 148	3,487,130	(128,707)	16,481	(500,230)
Total equity	2,865,023	$ 772	$ 148	3,504,494	$ (130,728)	12,085	(521,748)
Balance (in shares) at Dec. 31, 2018		77,226,443	14,841,431
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted share units issued to Trustees		1,156
Issuance of nonvested shares, net		197,755
Issuance of nonvested shares, net	(4,430)	$ (2)		(4,831)
Stock Issued During Period, Shares, Share-based Compensation, Forfeited					(403,000)
Purchase of common shares for vesting	(9,499)				$ (9,499)
Share-based compensation expense	(3,280)			(3,280)
Foreign currency translation adjustment	3,810					3,810
Change in unrealized loss on derivatives	(7,498)					(7,498)
Net income	65,349						65,349
Issuances of common shares (in shares)		1,064,600
Issuances of common shares	$ 78,993	$ 11		78,982
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	111,815	111,815
Stock Issued During Period, Value, Stock Options Exercised	$ 732	$ 1		5,543	6,276
Dividends to common and preferred shareholders	(84,343)						(84,343)	$ (1,939)	$ (1,939)	$ (1,939)			$ (1,939)	$ (2,156)	$ (2,156)
Balance (in shares) at Mar. 31, 2019		78,601,769	14,841,431
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total equity	$ 2,912,779	$ 786	$ 148	$ 3,597,130	$ (146,906)	$ 8,397	$ (546,776)