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]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total equity	$ 2,185,901	$ 663	$ 139	$ 2,677,046	$ (113,172)	$ 7,734	$ (386,509)
Balance (in shares) at Dec. 31, 2016		66,263,487	13,849,050
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of nonvested shares, net		283,154
Issuance of nonvested shares, net	(5,499)	$ (3)		(5,496)
Purchase of common shares for vesting	6,729				6,729
Amortization of nonvested shares	(3,264)			(3,264)
Share option expense	194			194
Foreign currency translation adjustment	1,674					1,674
Change in unrealized gain/loss on derivatives	(802)					(802)
Net income	53,916						53,916
Issuances of common shares (in shares)		931,870
Issuances of common shares	$ 68,201	$ 9		68,192
Stock option exercises, net (in shares)	17,391	17,391
Stock option exercises, net	$ (138)	$ 0		(916)	(1,054)
Dividends to common and preferred shareholders	(71,571)						(71,571)
Balance (in shares) at Mar. 31, 2017		67,495,902	13,849,050
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total equity	$ 2,239,409	$ 675	$ 139	$ 2,755,108	$ (120,955)	$ 8,606	$ (404,164)