Selected Quarterly Financial Information (Details 4) (USD $)	3 Months Ended								12 Months Ended			6 Months Ended	12 Months Ended	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	Jun. 30, 2012 Error attributable to the misapplication of U.S. GAAP	Dec. 31, 2011 Error attributable to the misapplication of U.S. GAAP	Sep. 30, 2012 Error attributable to the misapplication of U.S. GAAP Restatement adjustment	Dec. 31, 2012 Error attributable to the misapplication of U.S. GAAP Restatement adjustment
Overstated cumulative net income from continuing operations													$ 600,000
Understated cumulative net income from continuing operations												1,100,000
Income from continuing operations	$ (8,642,000)	$ 7,698,000	$ 11,011,000	$ 16,462,000	$ 23,588,000	$ 52,617,000	$ 56,318,000	$ 57,979,000	$ 26,529,000	$ 190,502,000	$ 277,176,000			$ 500,000	$ (600,000)