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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Abstract]
Net income (loss) available to common shareholders	$ 16,847	$ 19,882	$ 34,386	$ (123,127)
Weighted average common shares outstanding - Basic (in shares)	39,478	39,340	39,508	39,177
Dilutive effect of stock-based awards (in shares)	425	569	376	0
Weighted average common shares outstanding - Diluted (in shares)	39,903	39,909	39,884	39,177
Earnings (loss) per common share - Basic (in dollars per share)	$ 0.43	$ 0.51	$ 0.87	$ (3.14)
Earnings (loss) per common share - Diluted (in dollars per share)	$ 0.42	$ 0.50	$ 0.86	$ (3.14)