Basic Income Per Common Share and Diluted Income Per Common Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	1 Months Ended	3 Months Ended								12 Months Ended
	Jun. 30, 2010	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Basic Income Per Common Share and Diluted Income Per Common Share
Stated percentage of convertible debentures												0.75%
Income (numerator)
Net loss		$ (8,533)	$ (4,124)	$ 7,019	$ (6,932)	$ (158,449)	$ 8,704	$ (4,343)	$ 4,887	$ (12,570)	$ (149,201)	$ (39,879)
Shares (denominator)
Basic weighted-average common shares outstanding		92,187	92,125	92,069	91,886	91,277	91,844	93,552	93,993	92,068	92,666	92,701
Diluted weighted-average common shares outstanding		92,187	92,125	92,565	91,886	91,277	92,240	93,552	94,662	92,068	92,666	92,701
Basic and diluted per share amounts
Basic net (loss) per share		$ (0.09)	$ (0.04)	$ 0.08	$ (0.08)	$ (1.74)	$ 0.09	$ (0.05)	$ 0.05	$ (0.14)	$ (1.61)	$ (0.43)
Diluted net (loss) per share		$ (0.09)	$ (0.04)	$ 0.08	$ (0.08)	$ (1.74)	$ 0.09	$ (0.05)	$ 0.05	$ (0.14)	$ (1.61)	$ (0.43)
Convertible Debentures
Aggregate principal amount of convertible debentures												$ 9,943
Aggregate number of shares obligated to be issued upon conversion												342
Redemption price as percentage of principal amount	100.00%