Description of Business, Basis of Presentation, Corporate Transactions, Significant Accounting Policies, and Recent Accounting Pronouncements - Immaterial Correction of an Error in Previously Issued Financial Statements (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	Dec. 31, 2014
Error Corrections and Prior Period Adjustments Restatement [Line Items]
General and administrative					$ 2,879				$ 9,407	$ 9,667	$ 7,957
Total operating expenses					6,276				23,864	23,987	25,429
Operating income	$ 1,721	$ 2,810	$ 1,712	$ 1,101	938	$ 2,887	$ 925	$ 1,061	7,344	5,812	6,527
Income before income taxes					114				3,950	(3,799)	41,986
Income tax expense					(66)				601	1,287	(20,623)
Net income	$ 2,734	$ 1,203	$ 425	$ 189	$ 48	$ 1,285	$ (3,532)	$ (314)	$ 4,551	$ (2,512)	$ 21,363
Basic earnings (loss) per common share (in dollars per share)	$ 0.14	$ 0.06	$ 0.02	$ 0.01	$ 0.00	$ 0.07	$ (0.18)	$ (0.02)	$ 0.23	$ (0.13)	$ 1.17
Diluted earnings (loss) per common share (in dollars per share)	$ 0.14	$ 0.06	$ 0.02	$ 0.01	$ 0.00	$ 0.07	$ (0.18)	$ (0.02)	$ 0.23	$ (0.13)	$ 1.17
Deferred income tax liabilities, net	$ 3,114				$ 2,585				$ 3,114	$ 2,585
Total liabilities	223,708				223,830				223,708	223,830
Paid in capital	14,288				18,968				14,288	18,968
Retained earnings/(accumulated deficit)	376				(4,175)				376	(4,175)
Total shareholders' equity	$ 14,860				14,989				$ 14,860	14,989	$ 20,063	$ 27,680
Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
General and administrative					3,099					10,209
Total operating expenses					6,496					24,529
Operating income					718					5,270
Income before income taxes					(106)					(4,341)
Income tax expense					16					1,489
Net income					$ (90)					$ (2,852)
Basic earnings (loss) per common share (in dollars per share)					$ 0.00					$ (0.15)
Diluted earnings (loss) per common share (in dollars per share)					$ 0.00					$ (0.15)
Deferred income tax liabilities, net					$ 2,383					$ 2,383
Total liabilities					223,628					223,628
Paid in capital					19,510					19,510
Retained earnings/(accumulated deficit)					(4,515)					(4,515)
Total shareholders' equity					15,191					15,191
Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
General and administrative					(220)					(542)
Total operating expenses					(220)					(542)
Operating income					220					542
Income before income taxes					220					542
Income tax expense					(82)					(202)
Net income					$ 138					$ 340
Basic earnings (loss) per common share (in dollars per share)					$ 0.00					$ 0.02
Diluted earnings (loss) per common share (in dollars per share)					$ 0.00					$ 0.02
Deferred income tax liabilities, net					$ 202					$ 202
Total liabilities					202					202
Paid in capital					(542)					(542)
Retained earnings/(accumulated deficit)					340					340
Total shareholders' equity					$ (202)					$ (202)