Earnings Per Common Share - Computation of basic and diluted EPS (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
Basic earnings per common share:
Net income	$ (84,935)	$ 41,460	$ (60,825)	$ 85,827
Weighted-average basic common shares	43,318	35,089	38,439	35,268
Basic earnings per common share (in dollars per share)	$ (1.96)	$ 1.18	$ (1.58)	$ 2.43
Diluted earnings per share:
Net income	$ (84,935)	$ 41,460	$ (60,825)	$ 85,827
Weighted-average basic common shares	43,318	35,089	38,439	35,268
Effect of dilutive securities (in shares)		211		193
Weighted-average dilutive shares	43,318	35,300	38,439	35,461
Diluted earnings per common share (in dollars per share)	$ (1.96)	$ 1.17	$ (1.58)	$ 2.42