Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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Stockholders' Equity - Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income (loss)	$ (21,384)	$ 3,727	$ 1,498	$ 854	$ 3,026	$ 4,058	$ 3,451	$ 3,444	$ (15,306)	$ 13,979	$ 80,246
Basic and diluted weighted average common shares outstanding (shares)									20,210,260	20,586,066	21,471,041
Basic and diluted net (loss) income per common share (usd per share)	$ (1.07)	$ 0.19	$ 0.07	$ 0.04	$ 0.15	$ 0.20	$ 0.17	$ 0.17	$ (0.76)	$ 0.68	$ 3.74
Restricted Stock Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (shares)									90,665	0	0