CONDENSED CONSOLIDATED STATEMENT OF CHANGES IN EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Preferred Shares [Member]	Common Stock [Member]	Additional Paid-in-Capital [Member]	Accumulated Distributions in Excess of Net Income [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Non-controlling Interests [Member]
Beginning Balance at Dec. 31, 2015	$ 1,462,531	$ 94,016	$ 23	$ 2,776,837	$ (1,428,908)	$ (1,939)	$ 22,502
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchase of common shares	(8,973)			(8,973)
Issuance of common shares and deferred compensation amortization, net	5,925		1	5,924
Dividends/distributions	(42,104)				(41,415)		(689)
Net income	50,453				49,443		1,010
Other comprehensive income	(4,625)					(4,625)
Ending Balance at Mar. 31, 2016	1,463,207	94,016	24	2,773,788	(1,420,880)	(6,564)	22,823
Beginning Balance at Dec. 31, 2016	1,412,491	94,016	24	2,800,736	(1,500,966)	(1,033)	19,714
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common shares and deferred compensation amortization, net	18,322			18,322
Dividends/distributions	(44,331)				(43,291)		(1,040)
Net income	42,220				42,040		180
Other comprehensive income	1,292					1,292
Ending Balance at Mar. 31, 2017	$ 1,429,994	$ 94,016	$ 24	$ 2,819,058	$ (1,502,217)	$ 259	$ 18,854