Computation of Basic and Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Net income (loss) available to common shareholders	$ (62,802)	$ 19,446	$ (54,118)	$ 17,539
Weighted average common shares outstanding - Basic (in shares)	40,216	39,389	40,130	39,523
Dilutive effect of stock-based awards (in shares)	0	297	0	352
Weighted average common shares outstanding - Diluted (in shares)	40,216	39,686	40,130	39,875
Earnings (loss) per common share - Basic (in dollars per share)	$ (1.56)	$ 0.49	$ (1.35)	$ 0.44
Earnings (loss) per common share - Diluted (in dollars per share)	$ (1.56)	$ 0.49	$ (1.35)	$ 0.44