Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenue	$ 28,435	$ 26,114	$ 58,710	$ 53,984
Operating expenses:
Direct	11,939	10,734	24,439	22,273
Selling, general and administrative	6,905	7,270	13,591	14,627
Depreciation and amortization	1,139	1,092	2,244	2,060
Total operating expenses	19,983	19,096	40,274	38,960
Operating income	8,452	7,018	18,436	15,024
Other income (expense):
Interest income	15	11	29	22
Interest expense	(23)	(36)	(50)	(121)
Other, net	27	43	35	118
Total other income (expense)	19	18	14	19
Income before income taxes	8,471	7,036	18,450	15,043
Provision for income taxes	2,719	2,478	6,178	4,978
Net income	5,752	4,558	12,272	10,065
Common Class A [Member]
Other income (expense):
Net income	$ 2,855	$ 2,260	$ 6,088	$ 4,994
Basic Earnings Per Share:
Basic earnings per share (in dollars per share)	$ 0.14	$ 0.11	$ 0.29	$ 0.24
Diluted Earnings Per Share:
Diluted earnings per share (in dollars per share)	0.13	0.11	0.28	0.24
Dividends Per Share of Common Stock:
Dividends per share (in dollars per share)	$ 0.10	$ 0.08	$ 0.20	$ 0.16
Weighted average shares and share equivalents outstanding:
Weighted average shares and share equivalents outstanding, basic (in shares)	20,752	20,711	20,745	20,711
Weighted average shares and share equivalents outstanding, diluted (in shares)	21,525	20,992	21,404	21,002
Common Class B [Member]
Other income (expense):
Net income	$ 2,897	$ 2,298	$ 6,184	$ 5,071
Basic Earnings Per Share:
Basic earnings per share (in dollars per share)	$ 0.82	$ 0.65	$ 1.75	$ 1.44
Diluted Earnings Per Share:
Diluted earnings per share (in dollars per share)	0.80	0.64	1.71	1.41
Dividends Per Share of Common Stock:
Dividends per share (in dollars per share)	$ 0.60	$ 0.48	$ 1.20	$ 0.96
Weighted average shares and share equivalents outstanding:
Weighted average shares and share equivalents outstanding, basic (in shares)	3,514	3,508	3,514	3,498
Weighted average shares and share equivalents outstanding, diluted (in shares)	3,591	3,565	3,584	3,557