Unaudited Summarized Consolidated Quarterly Financial Data Unaudited Summarized Consolidated Quarterly Financial Data (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Data [Abstract]
Rental income	$ 206,104	[1]	$ 203,587	[1]	$ 200,959	[1]	$ 194,352	[1]	$ 190,321	[1]	$ 187,917	[1]	$ 186,285	[1]	$ 181,961	[1]
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	6,485		10,611		4,359		(5,195)		(3,374)		2,351		4,525		(1,162)		16,260	2,340	(46,305)
Income/(loss) from discontinued operations, net of tax	0		79		18		(87)		41,376		884		829		853		10	43,942	266,608
Net (loss)/income attributable to stakeholders	$ 64,486		$ 39,618		$ 29,076		$ 17,430		$ 35,769		$ 2,257		$ 4,261		$ (1,199)		$ 150,610	$ 41,088	$ 203,376
Earnings per weighted average common share - basic and diluted:
Net (loss)/income attributable to common stockholders — basic and diluted (in dollars per share)	$ 0.25	[2]	$ 0.16	[2]	$ 0.12	[2]	$ 0.07	[2]	$ 0.14	[2]	$ 0.01	[2]	$ 0.02	[2]	$ 0.00	[2]
Weighted Average Number of Shares Outstanding, Basic	253,983		251,655		250,255		250,177		249,987		249,985		249,985		249,917		251,528	249,969	238,851
Weighted average number of common shares outstanding — diluted	256,000		253,732		252,191		251,822		249,987		251,454		251,406		249,917		253,445	249,969	238,851

[1] Represents rental income from continuing operations, excluding amounts classified as discontinued operations.

[2] Quarterly income/(loss) per share amounts may not total to the annual amounts.