Earnings Per Share (Basic and Diluted Weighted Average Shares Outstanding and Earnings per Share) (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
Net income (loss)	$ 24,153	$ (2,247)	$ 35,401	$ 1,503	$ (7,341)	$ 23,458	$ 25,003	$ (14,509)	$ 58,810	$ 26,611	$ (8,468)
Net income attributable to participating securities									(455)	(77)
Net income (loss) attributable to common shares									58,355	26,534	(8,468)
Weighted average shares - basic									38,885	39,946	40,064
Dilutive effect of stock options									149	104
Weighted average shares - diluted									39,034	40,050	40,064
Basic earnings (loss) per share	$ 0.62	$ (0.06)	$ 0.90	$ 0.04	$ (0.19)	$ 0.59	$ 0.62	$ (0.36)	$ 1.50	$ 0.66	$ (0.21)
Diluted earnings (loss) per share	$ 0.61	$ (0.06)	$ 0.90	$ 0.04	$ (0.19)	$ 0.58	$ 0.62	$ (0.36)	$ 1.50	$ 0.66	$ (0.21)
Parent Company [Member]
Net income (loss)									$ 58,810	$ 26,611	$ (8,468)