Earnings Per Share - Computation of Basic and Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Earnings Per Share [Abstract]
Net income (loss) available to common shareholders	$ 14,620		$ 16,847		$ 19,446		$ (1,907)		$ 23,877		$ 19,882		$ 2,657		$ (145,666)		$ 49,006		$ (99,250)		$ 57,298
Weighted average common shares outstanding - Basic (in shares)																	39,556		39,244		38,655
Dilutive effect of stock-based awards (in shares)																	424		0		732
Weighted average common shares outstanding - Diluted (in shares)																	39,980		39,244		39,387
Earnings (loss) per common share - Basic (in dollars per share)	$ 0.37	[1]	$ 0.43	[1]	$ 0.49	[1]	$ (0.05)	[1]	$ 0.61	[1]	$ 0.51	[1]	$ 0.07	[1]	$ (3.74)	[1]	$ 1.24	[1]	$ (2.53)	[1]	$ 1.48
Earnings (loss) per common share - Diluted (in dollars per share)	$ 0.36	[1]	$ 0.42	[1]	$ 0.49	[1]	$ (0.05)	[1]	$ 0.60	[1]	$ 0.50	[1]	$ 0.07	[1]	$ (3.74)	[1]	$ 1.23	[1]	$ (2.53)	[1]	$ 1.45

[1] The sum of the quarterly EPS data presented in the table may not equal the annual results due to rounding and the impact of dilutive securities on the annual versus the quarterly EPS calculations.