General Information (Details) (USD $) In Thousands, except Per Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Income (loss):
Net income (loss) attributable to common stockholders	$ 13,291	$ (90,731)	$ 12,124	$ (69,188)
Less: Undistributed income allocated to participating securities	(121)		(141)
Basic	13,170	(90,731)	11,983	(69,188)
Undistributed income allocated to participating securities	121		141
Undistributed income reallocated to participating securities	(120)		(140)
Diluted	$ 13,171	$ (90,731)	$ 11,984	$ (69,188)
Shares:
Weighted-average common shares outstanding, basic	25,829	25,546	25,754	25,470
Dilutive effect of stock options and restricted stock awards	120	0	131	0
Diluted	25,949	25,546	25,885	25,470
Income (loss) per common share:
Basic	$ 0.51	$ (3.55)	$ 0.47	$ (2.72)
Diluted	$ 0.51	$ (3.55)	$ 0.46	$ (2.72)