Earnings (Loss) Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Earnings (Loss) Per Share
Net income (loss) for basic and diluted earnings per share (in dollars)	$ 9,662	$ 7,715	$ 5,086	$ 8,622	$ (6,453)	$ 232	$ (247,096)	$ 5,458	$ 31,085	$ (247,859)	$ (179,789)
Shares of common stock and common stock equivalents:
Weighted average shares-basic	36,287,000	36,544,000	36,956,000	37,378,000	37,709,000	38,301,000	38,607,000	39,112,000	36,788,000	38,418,000	40,691,000
Effect of dilutive securities (in shares)									1,326,000
Weighted average shares-diluted	37,685,000	37,781,000	38,000,000	38,615,000	37,709,000	39,252,000	38,607,000	40,303,000	38,114,000	38,418,000	40,691,000
Earnings (loss) per share:
Basic (in dollars per share)	$ 0.27	$ 0.21	$ 0.14	$ 0.23	$ (0.17)	$ 0.01	$ (6.40)	$ 0.14	$ 0.84	$ (6.45)	$ (4.42)
Diluted (in dollars per share)	$ 0.26	$ 0.20	$ 0.13	$ 0.22	$ (0.17)	$ 0.01	$ (6.40)	$ 0.14	$ 0.82	$ (6.45)	$ (4.42)
Anti-dilutive equity awards not included in the detailed earnings per share computation
Equity awards not included in the diluted earnings per share computation									200,000	3,600,000	3,600,000