Computation 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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share [Abstract]
Net income (loss) available to common shareholders	$ (25,357)	$ 16,847	$ (79,475)	$ 34,386
Weighted average common shares outstanding - Basic (in shares)	40,337	39,478	40,199	39,508
Dilutive effect of stock-based awards (in shares)	0	425	0	376
Weighted average common shares outstanding - Diluted (in shares)	40,337	39,903	40,199	39,884
Earnings (loss) per common share - Basic (in dollars per share)	$ (0.63)	$ 0.43	$ (1.98)	$ 0.87
Earnings (loss) per common share - Diluted (in dollars per share)	$ (0.63)	$ 0.42	$ (1.98)	$ 0.86