Consolidated Statements of Changes in Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Common Stock Common Class A	Common Stock Common Class B	Additional Paid In Capital	Treasury Stock Common Class A	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Total
Balance at the beginning of the period at Dec. 31, 2014	$ 1	$ 3	$ 246,858	$ (1,961)	$ 12,098	$ (586)	$ 256,413
Balance at the beginning of the period (in shares) at Dec. 31, 2014	14,519	30,027
Consolidated Statements of Changes in Stockholders' Equity
Net income (loss)					13,739		13,739
Issuance of restricted stock			2,522	(1,183)			1,339
Issuance of restricted stock (in shares)	324
Excess tax benefits related to the issuance of restricted stock			272				272
Stock-based compensation			3,053				3,053
Issuance of Class A common stock			5,407				5,407
Issuance of Class A common stock (in shares)	479
Repurchase of warrants			(1,778)				(1,778)
Exercise of warrants			60				60
Exercise of warrants (in shares)	5
Exercise of stock options			157				157
Exercise of stock options (in shares)	15
Other comprehensive income (loss), net of tax						(21)	(21)
Balance at the end of the period at Dec. 31, 2015	$ 1	$ 3	256,551	(3,144)	25,837	(607)	278,641
Balance at the end of the period (in shares) at Dec. 31, 2015	15,342	30,027
Consolidated Statements of Changes in Stockholders' Equity
Net income (loss)					18,000		18,000
Issuance of restricted stock			934	(1,190)			(256)
Issuance of restricted stock (in shares)	328
Excess tax benefits related to the issuance of restricted stock			210				210
Stock-based compensation			3,757				3,757
Repurchase of Class A common stock				(30,735)			(30,735)
Conversion of Class B common stock to Class A common stock	$ 1	$ (1)
Conversion of Class B common stock to Class A common stock (in shares)	9,226	(9,226)
Repurchase of warrants			(976)				(976)
Exercise of warrants			420				420
Exercise of warrants (in shares)	35
Exercise of stock options			155				155
Exercise of stock options (in shares)	13
Other comprehensive income (loss), net of tax						124	124
Balance at the end of the period at Dec. 31, 2016	$ 2	$ 2	261,051	(35,069)	43,837	(483)	269,340
Balance at the end of the period (in shares) at Dec. 31, 2016	24,944	20,801
Consolidated Statements of Changes in Stockholders' Equity
Net income (loss)					(13,436)		(13,436)
Issuance of restricted stock	$ 1		1,155	(324)			832
Issuance of restricted stock (in shares)	204
Stock-based compensation			2,912				2,912
Repurchase of Class A common stock				(21,910)			(21,910)
Exercise of warrants			211				211
Exercise of warrants (in shares)	23
Other comprehensive income (loss), net of tax						955	955
Balance at the end of the period at Dec. 31, 2017	$ 3	$ 2	$ 265,329	$ (57,303)	$ 30,401	$ 472	$ 238,904
Balance at the end of the period (in shares) at Dec. 31, 2017	25,171	20,801