Earnings Per Share - (Computations for Basic and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Net income	$ 2,105	$ 8,960	$ 10,919	$ 42,947
Weighted-average common shares outstanding — basic	65,646	64,864	65,458	64,659
Effect of stock options and restricted stock units	491	894	729	1,143
Weighted-average common shares outstanding — diluted	66,137	65,758	66,187	65,802
Basic earnings per share	$ 0.03	$ 0.14	$ 0.17	$ 0.66
Diluted earnings per share	$ 0.03	$ 0.14	$ 0.16	$ 0.65