Net Income Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Computation of basic and diluted net loss per share [Abstract]
Net income	$ 17,457	$ 3,321	$ 29,853	$ 6,493
Denominator for basic earnings per share - weighted average shares (in shares)	106,871,436	105,991,990	106,469,278	105,927,890
Effect of dilutive securities: Stock options and restricted stock outstanding (in shares)	10,630,489	6,369,189	10,077,728	6,265,811
Denominator for diluted earnings per share - weighted average shares adjusted for dilutive securities (in shares)	117,501,925	112,361,179	116,547,006	112,193,701
Income per common share - basic (in dollars per share)	$ 0.16	$ 0.03	$ 0.28	$ 0.06
Income per common share - diluted (in dollars per share)	$ 0.15	$ 0.03	$ 0.26	$ 0.06
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	10,630,489	6,369,189	10,077,728	6,265,811
Outstanding stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	7,916,564	5,704,112	7,985,521	5,767,469
Restricted stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	2,713,925	665,077	2,092,207	498,342