Summary of Quarterly Results (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 Information [Line Items]
Total revenue	$ 147,810	$ 146,558	$ 150,500	$ 152,114	$ 138,658	$ 143,354	$ 140,664	$ 139,554	$ 596,982	$ 562,210	$ 535,679
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(1,869)	8,882	2,174	(2,245)	21,002	11,088	7,180	3,919	6,942	43,189	6,529
Net Income (Loss) Attributable to Parent	$ (3,585)	$ 6,967	$ 385	$ (4,041)	$ 18,975	$ 9,173	$ 5,308	$ 2,058	$ 6,975	$ 42,777	$ 6,595
Earnings Per Share, Basic	$ (0.02)	$ 0.04	$ 0.00	$ (0.03)	$ 0.12	$ 0.06	$ 0.03	$ 0.01	$ 0.00	$ 0.23	$ (0.06)
Earnings Per Share, Diluted	$ (0.02)	$ 0.04	$ 0.00	$ (0.03)	$ 0.12	$ 0.06	$ 0.03	$ 0.01	$ 0.00	$ 0.23	$ (0.06)