Quarterly Operating Results (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Quarterly Financial Data [Abstract]
Total revenues	$ 104,742	$ 104,305	$ 94,167	$ 77,474	$ 84,409	$ 87,803	$ 73,110	$ 42,665	$ 380,688	$ 287,987	$ 57,761
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	7,213	12,105	10,027	(2,837)	8,106	5,838	4,299	(3,044)	26,508	15,199	(6,642)
Net Income (Loss) Attributable to Parent	7,088	11,918	9,864	(2,791)	7,962	5,724	4,214	(3,044)	26,079	14,856	(6,642)
Net income (loss) attributable to common shareholders	$ 2,632	$ 7,462	$ 5,407	$ (7,247)	$ 3,456	$ 2,825	$ 1,753	$ (3,591)	$ 8,254	$ 4,443	$ (6,642)
Earnings Per Share, Basic and Diluted	$ 0.04	$ 0.13	$ 0.10	$ (0.14)	$ 0.07	$ 0.05	$ 0.03	$ (0.09)	$ 0.14	$ 0.08	$ (0.23)