Income Taxes - Significant Components of Income Tax Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current provision:
Federal	$ 1,535	$ (72)	$ 8,576
State	977	453	1,270
Deferred provision:
Federal	1,070	4,144	(2,421)
State	351	(472)	(277)
Total income tax provision	$ 3,933	$ 4,053	$ 7,148