Condensed Consolidated Statements of Equity (Unaudited) - 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] Retained Earnings [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Parent [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member] Noncontrolling Interest [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]	Retained Earnings [Member]	Parent [Member]	Noncontrolling Interest [Member]	Common Class B [Member]	Total
Balance (in shares) at Dec. 31, 2018								28,696,321	35,452,178
Balance at Dec. 31, 2018	$ 0	$ 0	$ 0	$ 67	$ 67	$ 99	$ 166	$ 29	$ 35	$ 517,073	$ (182,497)	$ 334,640	$ 491,852		$ 826,492
Stock-based compensation expense								$ 0	$ 0	2,212	0	2,212	0		2,212
Vesting of restricted stock units, net of taxes paid (in shares)								166,140	0
Vesting of restricted stock units, net of taxes paid								$ 0	$ 0	0	0	0	0		0
Vested restricted stock units retained by the Company in exchange for payment of recipient mandatory tax withholdings (in shares)								59,261	0
Vested restricted stock units retained by the Company in exchange for payment of recipient mandatory tax withholdings								$ 0	$ 0	(396)	0	(396)	0		(396)
Cancellation of treasury shares (in shares)								(59,261)	0
Net income (loss)								$ 0	$ 0	0	(17,204)	(17,204)	(21,239)		(38,443)
Balance (in shares) at Mar. 31, 2019								28,862,461	35,452,178
Balance at Mar. 31, 2019								$ 29	$ 35	518,889	(199,634)	319,319	470,712		790,031
Balance (in shares) at Dec. 31, 2018								28,696,321	35,452,178
Balance at Dec. 31, 2018	$ 0	$ 0	$ 0	$ 67	$ 67	$ 99	$ 166	$ 29	$ 35	517,073	(182,497)	334,640	491,852		826,492
Class B Common Stock converted to Class A Common Stock (in shares)														35,732
Net income (loss)															7,220
Balance (in shares) at Sep. 30, 2019								29,150,220	35,416,446
Balance at Sep. 30, 2019								$ 29	$ 35	523,402	(179,087)	344,379	495,352		839,731
Balance (in shares) at Mar. 31, 2019								28,862,461	35,452,178
Balance at Mar. 31, 2019								$ 29	$ 35	518,889	(199,634)	319,319	470,712		790,031
Stock-based compensation expense								$ 0	$ 0	2,261	0	2,261			2,261
Vesting of restricted stock units, net of taxes paid (in shares)								133,311	0
Vesting of restricted stock units, net of taxes paid								$ 0	$ 0	0	0	0	0		0
Vested restricted stock units retained by the Company in exchange for payment of recipient mandatory tax withholdings (in shares)								43,344	0
Vested restricted stock units retained by the Company in exchange for payment of recipient mandatory tax withholdings								$ 0	$ 0	(265)	0	(265)	0		(265)
Cancellation of treasury shares (in shares)								(43,344)	0
Class B Common Stock converted to Class A Common Stock (in shares)								35,732
Conversion of Stock, Shares Converted (in shares)									(35,732)
Class B Common Stock converted to Class A Common Stock								$ 0	$ 0	476	0	476			0
Class B Common Stock converted to Class A Common Stock													(476)
Net income (loss)								$ 0	$ 0	0	8,777	8,777	10,759		19,536
Balance (in shares) at Jun. 30, 2019								29,031,504	35,416,446
Balance at Jun. 30, 2019								$ 29	$ 35	521,361	(190,857)	330,568	480,995		811,563
Stock-based compensation expense								$ 0	$ 0	2,207	0	2,207			2,207
Vesting of restricted stock units, net of taxes paid (in shares)								118,716	0
Vesting of restricted stock units, net of taxes paid								$ 0	$ 0	0	0	0	0		0
Vested restricted stock units retained by the Company in exchange for payment of recipient mandatory tax withholdings (in shares)								49,111	0
Vested restricted stock units retained by the Company in exchange for payment of recipient mandatory tax withholdings								$ 0	$ 0	(166)	0	(166)	0		(166)
Cancellation of treasury shares (in shares)								(49,111)	0
Class B Common Stock converted to Class A Common Stock (in shares)								0						35,732
Conversion of Stock, Shares Converted (in shares)									0
Class B Common Stock converted to Class A Common Stock								$ 0	$ 0	0	0	0			0
Class B Common Stock converted to Class A Common Stock													0
Net income (loss)								$ 0	$ 0	0	11,770	11,770	14,357		26,127
Balance (in shares) at Sep. 30, 2019								29,150,220	35,416,446
Balance at Sep. 30, 2019								$ 29	$ 35	523,402	(179,087)	344,379	495,352		839,731
Balance (in shares) at Dec. 31, 2019								29,421,131	35,260,680
Balance at Dec. 31, 2019								$ 29	$ 35	527,246	(181,711)	345,599	490,152		835,751
Stock-based compensation expense								$ 0	$ 0	2,694	0	2,694			2,694
Vesting of restricted stock units, net of taxes paid (in shares)								231,834	0
Vesting of restricted stock units, net of taxes paid								$ 1	$ 0	0	0	1	0		1
Vested restricted stock units retained by the Company in exchange for payment of recipient mandatory tax withholdings (in shares)								75,695	0
Vested restricted stock units retained by the Company in exchange for payment of recipient mandatory tax withholdings								$ 0	$ 0	(214)	0	(214)	0		(214)
Cancellation of treasury shares (in shares)								(75,695)	0
Class B Common Stock converted to Class A Common Stock (in shares)								199,993
Conversion of Stock, Shares Converted (in shares)									(199,993)
Class B Common Stock converted to Class A Common Stock								$ 0	$ 0	2,897	0	2,897			0
Class B Common Stock converted to Class A Common Stock													(2,897)
Net income (loss)								$ 0	$ 0	0	16,708	16,708	20,006		36,714
Balance (in shares) at Mar. 31, 2020								29,852,958	35,060,687
Balance at Mar. 31, 2020								$ 30	$ 35	532,623	(165,003)	367,685	507,261		874,946
Balance (in shares) at Dec. 31, 2019								29,421,131	35,260,680
Balance at Dec. 31, 2019								$ 29	$ 35	527,246	(181,711)	345,599	490,152		835,751
Class B Common Stock converted to Class A Common Stock (in shares)														251,309
Net income (loss)															(11,053)
Balance (in shares) at Sep. 30, 2020								30,210,749	35,009,371
Balance at Sep. 30, 2020								$ 30	$ 35	537,990	(186,787)	351,268	480,565		831,833
Balance (in shares) at Mar. 31, 2020								29,852,958	35,060,687
Balance at Mar. 31, 2020								$ 30	$ 35	532,623	(165,003)	367,685	507,261		874,946
Stock-based compensation expense								$ 0	$ 0	2,568	0	2,568	0		2,568
Vesting of restricted stock units, net of taxes paid (in shares)								165,399	0
Vesting of restricted stock units, net of taxes paid								$ 0	$ 0	0	0	0	0		0
Vested restricted stock units retained by the Company in exchange for payment of recipient mandatory tax withholdings (in shares)								57,810	0
Vested restricted stock units retained by the Company in exchange for payment of recipient mandatory tax withholdings								$ 0	$ 0	(170)	0	(170)	0		(170)
Cancellation of treasury shares (in shares)								(57,810)	0
Class B Common Stock converted to Class A Common Stock (in shares)								2,000
Conversion of Stock, Shares Converted (in shares)									(2,000)
Class B Common Stock converted to Class A Common Stock								$ 0	$ 0	28	0	28			0
Class B Common Stock converted to Class A Common Stock													(28)
Net income (loss)								$ 0	$ 0	0	(16,339)	(16,339)	(19,570)		(35,909)
Balance (in shares) at Jun. 30, 2020								30,020,357	35,058,687
Balance at Jun. 30, 2020								$ 30	$ 35	535,049	(181,342)	353,772	487,663		841,435
Stock-based compensation expense								$ 0	$ 0	2,403	0	2,403	0		2,403
Vesting of restricted stock units, net of taxes paid (in shares)								141,076	0
Vesting of restricted stock units, net of taxes paid								$ 0	$ 0	0	0	0	0		0
Vested restricted stock units retained by the Company in exchange for payment of recipient mandatory tax withholdings (in shares)								54,268	0
Vested restricted stock units retained by the Company in exchange for payment of recipient mandatory tax withholdings								$ 0	$ 0	(147)	0	(147)	0		(147)
Cancellation of treasury shares (in shares)								(54,268)	0
Class B Common Stock converted to Class A Common Stock (in shares)								49,316						49,316
Conversion of Stock, Shares Converted (in shares)									(49,316)
Class B Common Stock converted to Class A Common Stock								$ 0	$ 0	685	0	685			0
Class B Common Stock converted to Class A Common Stock													(685)
Net income (loss)								$ 0	$ 0	0	(5,445)	(5,445)	(6,413)		(11,858)
Balance (in shares) at Sep. 30, 2020								30,210,749	35,009,371
Balance at Sep. 30, 2020								$ 30	$ 35	$ 537,990	$ (186,787)	$ 351,268	$ 480,565		$ 831,833