Earnings Per Share - Reconciliation of the Numerator and Denominator of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Numerator [Abstract]
Income from continuing operations - numerator for earnings per share	$ 13,920	$ 25,357	$ 36,271	$ 69,375
Income from discontinued operations - numerator for earnings per share				901
Net income allocated to unvested restricted stock	(63)		(140)
Net income allocated to shares of Common Stock	$ 13,857	$ 25,357	$ 36,131	$ 70,276
Denominator [Abstract]
Shares used for basic income per share	47,923	40,010	45,996	39,898
Effect of dilutive stock options and restricted stock units outstanding [Abstract]
Shares used for diluted income per share	48,584	42,827	46,585	43,234
Earnings per share - basic:
Continuing operations	$ 0.29	$ 0.63	$ 0.79	$ 1.74
Discontinued operations				0.02
Net income	0.29	0.63	0.79	1.76
Earnings per share - diluted:
Continuing operations	0.29	0.59	0.78	1.60
Discontinued operations				0.02
Net income	$ 0.29	$ 0.59	$ 0.78	$ 1.63
Non-Qualified Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Dilutive securities outstanding not included in the computation of earnings (loss) per share because their effect is anti-dilutive (in shares)	70	81	74	47
Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Dilutive securities outstanding not included in the computation of earnings (loss) per share because their effect is anti-dilutive (in shares)	276	47	207	34
Non-Qualified Stock Options
Effect of dilutive stock options and restricted stock units outstanding [Abstract]
Effect of dilutive stock options and restricted stock units outstanding (in shares)	64	242	94	277
Restricted Stock Units
Effect of dilutive stock options and restricted stock units outstanding [Abstract]
Effect of dilutive stock options and restricted stock units outstanding (in shares)	597	263	495	333
Market Stock Units
Effect of dilutive stock options and restricted stock units outstanding [Abstract]
Effect of dilutive stock options and restricted stock units outstanding (in shares)		468		497
Warrants Related to Cash Convertible Notes
Effect of dilutive stock options and restricted stock units outstanding [Abstract]
Effect of dilutive stock options and restricted stock units outstanding (in shares)		1,844		2,229
Restricted Stock Awards
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Dilutive securities outstanding not included in the computation of earnings (loss) per share because their effect is anti-dilutive (in shares)	156		94