Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income	$ 3,644	$ 2,653	$ 21,712	$ 3,302
Basic - weighted average common shares outstanding (in shares)	90,526	85,426	89,779	84,749
Dilutive effect of stock options and restricted stock awards (in shares)	2,151	2,251	2,535	2,545
Weighted average common shares outstanding - diluted (in shares)	93,582	87,677	93,041	87,294
Income per common share - basic (in dollars per share)	$ 0.04	$ 0.03	$ 0.24	$ 0.04
Income per common share - diluted (in dollars per share)	$ 0.04	$ 0.03	$ 0.23	$ 0.04
Stock options and restricted stock excluded from calculation of diluted earnings per share because anti-dilutive for the period (in shares)	735	1,693	1,184	2,149
Convertible debt \| Convertible Notes due 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive effect of Convertible Notes (in shares)	905	0	727	0
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
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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