Real Estate Investments Real Estate Investments, Pro Forma of Acquired Properties (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pro Forma [Abstract]
Business Acquisition, Pro Forma Revenue									$ 610,979	$ 592,753
Business Acquisition, Pro Forma Income (Loss) from Continuing Operations before Changes in Accounting and Extraordinary Items, Net of Tax									21,805	(60,011)
Business Acquisition, Pro Forma Net Income (Loss)									$ 25,957	$ (16,970)
Continuing operations (in dollars per share)									$ 0.20	$ (0.36)	$ (0.24)
Business Acquisition, Pro Forma Income (Loss) from Continuing Operations before Changes in Accounting and Extraordinary Items, Net of Tax, Per Share, Basic									$ 0.14	$ (0.42)
Income (Loss) from Continuing Operations, Per Diluted Share									$ 0.20	$ (0.36)	$ (0.24)
Business Acquisition, Pro Forma Income (Loss) from Continuing Operations before Changes in Accounting and Extraordinary Items, Net of Tax, Per Share, Diluted									$ 0.14	$ (0.42)
Earnings Per Share, Basic	$ 0.12	$ 0.06	$ 0.03	$ 0.01	$ (0.21)	$ 0.10	$ 0.01	$ 0.05	$ 0.23	$ (0.06)	$ (0.10)
Pro Forma, Earnings Per Share, Basic									$ 0.17	$ (0.12)
Earnings Per Share, Diluted	$ 0.12	$ 0.06	$ 0.03	$ 0.01	$ (0.21)	$ 0.10	$ 0.01	$ 0.05	$ 0.23	$ (0.06)	$ (0.10)
Pro Forma Earnings Per Share, Diluted									$ 0.17	$ (0.12)