Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue	$ 127,982	$ 119,686	$ 117,559
Direct, exclusive of depreciation and amortization	46,435	47,577	49,068
Selling, general and administrative, exclusive of depreciation and amortization	32,973	31,371	29,686
Depreciation and amortization	5,539	5,463	4,586
Total operating expenses	84,947	84,411	83,340
Operating income	43,035	35,275	34,219
Interest income	37	62	96
Interest expense	(2,091)	(1,513)	(82)
Other, net	(462)	885	50
Total other income (expense)	(2,516)	(566)	64
Income before income taxes	40,519	34,709	34,283
Provision for income taxes	8,113	4,662	11,340
Net income	$ 32,406	$ 30,047	$ 22,943
Common Class A [Member]
Basic earnings per share:
Basic earnings per share (in dollars per share)	$ 1.30	$ 1.08	$ 0.54
Diluted earnings per share:
Diluted earnings per share (in dollars per share)	$ 1.26	$ 1.04	$ 0.52
Weighted average shares and share equivalents outstanding
Weighted average shares and share equivalents outstanding, basic (in shares)	24,809	23,562	20,770
Weighted average shares and share equivalents outstanding, diluted (in shares)	25,653	24,448	21,627
Common Class B [Member]
Net income		$ 4,624	$ 11,555
Basic earnings per share:
Basic earnings per share (in dollars per share)		$ 1.31	$ 3.26
Diluted earnings per share:
Diluted earnings per share (in dollars per share)		$ 1.27	$ 3.18
Weighted average shares and share equivalents outstanding
Weighted average shares and share equivalents outstanding, basic (in shares)		3,527	3,514
Weighted average shares and share equivalents outstanding, diluted (in shares)		3,628	3,603