Net Income per Share - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ 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 (loss) income	$ (134,779)	$ 21,390	$ (112,451)	$ 53,033
Less: Net loss (income) allocated to unvested participating restricted stock	4,763	(719)	3,961	(1,827)
Net (loss) income available to common stockholders - basic	(130,016)	20,671	(108,490)	51,206
Dilutive Securities, Effect on Basic Earnings Per Share, Options and Restrictive Stock Units	3	7	0	20
Net (loss) income available to common stockholders - diluted	$ (130,013)	$ 20,678	$ (108,490)	$ 51,226
Weighted average outstanding shares of common stock - basic (in shares)	16,177,000	17,181,000	16,215,000	17,262,000
Dilutive effect of stock options (in shares)	0	382,000	0	364,000
Weighted average outstanding shares of common stock - diluted (in shares)	16,177,000	17,563,000	16,215,000	17,626,000
Net income per common share - basic (USD per share)	$ (8.04)	$ 1.20	$ (6.69)	$ 2.97
Net income per common share - diluted (USD per share)	$ (8.04)	$ 1.18	$ (6.69)	$ 2.91
Antidilutive securities excluded from computation of earnings per share (in shares)			101,000