Unaudited Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Total gross revenues	$ 106,626	$ 105,438	$ 110,333	$ 108,442	$ 107,783	[1]	$ 106,572	[1]	$ 105,447	[1]	$ 104,016	[1]	$ 430,839	$ 423,818	$ 361,055
Net income	35,513	(5,200)	50,207	34,371	38,185		42,177		15,287		1,814		114,891	97,463	3,863
Net income (loss) attributable to common shareholders	$ 33,229	$ (7,629)	$ 47,654	$ 31,829	$ 35,700		$ 38,720		$ 12,743		$ (839)		$ 111,703	$ 93,104	$ 1,630
Net income (loss) attributable to common shareholders - basic (in dollars per share)	$ 0.14	$ (0.03)	$ 0.20	$ 0.14	$ 0.15		$ 0.17		$ 0.05		$ 0.00		$ 0.45	$ 0.38	$ (0.07)
Net income (loss) attributable to common shareholders - diluted (in dollars per share)	$ 0.14	$ (0.03)	$ 0.20	$ 0.14	$ 0.15		$ 0.17		$ 0.05		$ 0.00		$ 0.45	$ 0.38	$ (0.07)

[1] All periods have been adjusted to reflect the impact of properties sold during the years ended December 31, 2014, and properties classified as held for sale as of December 31, 2014, which are reflected in discontinued operations in the Consolidated Statements of Operations.