Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Cumulative Effect, Period of Adoption, Adjustment [Member] Common Stock [Member] Common Class A [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Common Stock [Member] Common Class B [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Additional Paid-in Capital [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Treasury Stock [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] AOCI Attributable to Parent [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Retained Earnings [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member]	Common Stock [Member] Common Class A [Member]	Common Stock [Member] Common Class B [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Total
Balances at Dec. 31, 2017	$ 0	$ 0	$ 0	$ 0	$ 0	$ 592	$ 592	$ 171	$ 24	$ 137,242	$ 0	$ 293	$ 157,471	$ 295,201
Net (loss) income								0	0	0	0	0	42,503	42,503
Other comprehensive loss								0	0	0	0	(89)	0	(89)
Stock-based employee compensation expense								0	0	4,802	0	0	0	4,802
Issuance of restricted shares, net								0	0	133	0	0	0	133
Balances at Dec. 31, 2018								171	24	142,177	0	204	200,566	343,142
Net (loss) income								0	0	0	0	0	8,477	8,477
Other comprehensive loss								0	0	0	0	(1,218)	0	(1,218)
Stock-based employee compensation expense								0	0	819	0	0	0	819
Issuance of restricted shares, net								2	0	(1,111)	0	0	0	(1,109)
Balances at Dec. 31, 2019								173	24	141,885	0	(1,014)	209,043	350,111
Net (loss) income								0	0	0	0	0	(42,718)	(42,718)
Other comprehensive loss								0	0	0	0	(1,237)	0	(1,237)
Stock-based employee compensation expense								0	0	2,270	419	0	0	2,689
Issuance of restricted shares, net								0	0	(717)	0	0	0	(717)
Share repurchase								0	0	0	(17,486)	0	0	(17,486)
Balances at Dec. 31, 2020								$ 173	$ 24	$ 143,438	$ (17,067)	$ (2,251)	$ 166,325	$ 290,642