Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income	$ 10,846	$ 1,632	$ 18,068	$ 649
Basic - weighted average common shares outstanding (in shares)	89,703	84,653	89,400	84,404
Dilutive effect of stock options and restricted stock awards (in shares)	2,823	2,662	2,730	2,695
Weighted average common shares outstanding - diluted (in shares)	93,791	87,315	92,766	87,099
Income per common share - basic (in dollars per share)	$ 0.12	$ 0.02	$ 0.20	$ 0.01
Income per common share - diluted (in dollars per share)	$ 0.12	$ 0.02	$ 0.19	$ 0.01
Stock options and restricted stock excluded from calculation of diluted earnings per share because anti-dilutive for the period (in shares)	1,173	2,464	1,412	2,381
Convertible debt \| Convertible Notes due 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stock options and restricted stock excluded from calculation of diluted earnings per share because anti-dilutive for the period (in shares)	0	7,569	0	7,569
Convertible debt \| Convertible Notes due 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive effect of Convertible Notes (in shares)	1,265	0	636	0
Stock options and restricted stock excluded from calculation of diluted earnings per share because anti-dilutive for the period (in shares)	0	0	0	0
Senior notes \| Convertible Notes due 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Debt instrument, convertible, conversion price (in dollars per share)	$ 9.33		$ 9.33

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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