(Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Earning per share reconciliation
Net (loss) income	$ (32,296)	$ (28,717)	$ (10,409)	$ 12,200	$ (61,013)	$ 1,791
Weighted-average common shares outstanding (in shares)	78,987		78,635		78,787	78,436
[(Loss) earnings] per share, basic (in dollars per share)	$ (0.41)		$ (0.13)		$ (0.77)	$ 0.02
Net (loss) income	$ (32,296)	$ (28,717)	$ (10,409)	$ 12,200	$ (61,013)	$ 1,791
Effect of dilutive securities (in shares)	0		0		0	4,811
Weighted-average common shares outstanding, assuming dilution (in shares)	78,987		78,635		78,787	83,247
[(Loss) earnings] per share, diluted (in dollars per share)	$ (0.41)		$ (0.13)		$ (0.77)	$ 0.02
Outstanding anti-dilutive stock options and RSUs (in shares)	6,253		6,500		5,908	242
Stock Options
Earning per share reconciliation
Weighted-average effect of dilutive securities (in shares)	0		0		0	3,132
RSUs
Earning per share reconciliation
Weighted-average effect of dilutive securities (in shares)	0		0		0	1,679