Components of Calculation of Basic and Diluted Earnings Per Share (Details) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income (loss)		$ (2,521)	$ 21,329	$ 7,774	$ 49,410
Weighted-average shares – basic		15,058	14,992	15,050	14,992
Effect of dilutive securities	[1]	0	58	121	105
Weighted-average shares – diluted		15,058	15,050	15,171	15,097
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		100

[1] For the three months ended June 30, 2018, approximately 0.1 million potentially dilutive securities, represented by RSUs and PRSUs, had the effect of being anti-dilutive and were excluded from the calculation of diluted earnings per share.