Summary of Significant Accounting Policies and Related Matters - Summary of Net Income (Loss) Available to Common Stockholders and the Net Income (Loss) Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Summary of net income available to common stockholders and the net income per common share
Net income (loss)	$ 19,621	$ (16,342)
Net income (loss) per common share:
Basic	$ 2.70	$ (2.25)
Diluted	$ 2.70	$ (2.25)
Weighted average common shares outstanding:
Basic	7,267	7,267
Diluted	7,267	7,267