Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Earnings Per Share
Net income (loss) for basic and diluted earnings (loss) per share (in dollars)	$ 5,086	$ (247,096)	$ 13,708	$ (241,638)
Shares of common stock and common stock equivalents:
Average common shares used in basic computation	36,956	38,607	37,166	38,859
Effect of dilutive securities (in shares)	1,044		1,205
Average common shares used in diluted computation	38,000	38,607	38,371	38,859
Earnings (loss) per share:
Basic (in dollars per share)	$ 0.14	$ (6.40)	$ 0.37	$ (6.22)
Diluted (in dollars per share)	$ 0.13	$ (6.40)	$ 0.36	$ (6.22)
Anti-dilutive equity awards not included in the detailed earnings per share computation
Equity awards not included in the diluted earnings per share computation	385	3,659	450	3,634

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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