Computation of Net Income (Loss) Per Share - Calculations Of Basic And Diluted (Loss) Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Numerator:
Net income (loss) used for calculating basic and diluted income (loss) per common share	$ 20,795	$ (19,587)
Denominator:
Weighted average number of common shares used in the calculation of basic (loss) income per share (in shares)	89,882	91,005
Common stock equivalents associated with stock-based compensation plans (in shares)	1,122	0
Shares used in the calculation of diluted (loss) income per share (in shares)	91,004	91,005
Basic (loss) income per share (in dollars per share)	$ 0.23	$ (0.22)
Diluted (loss) income per share (in dollars per share)	$ 0.23	$ (0.22)