Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue	$ 31,017	$ 30,276
Operating expenses:
Direct	12,909	12,500
Selling, general and administrative	7,867	6,686
Depreciation and amortization	1,283	1,106
Total operating expenses	22,059	20,292
Operating income	8,958	9,984
Other income (expense):
Interest income	45	14
Interest expense	(8)	(27)
Other, net	(28)	9
Total other income (expense)	9	(4)
Income before income taxes	8,967	9,980
Provision for income taxes	1,661	3,459
Net income	7,306	6,521
Common Class A [Member]
Other income (expense):
Net income	$ 3,630	$ 3,234
Denominator for net income per share - basic:
Basic earnings per share (in dollars per share)	$ 0.17	$ 0.15
Numerator for net income per share - diluted:
Diluted earnings per share (in dollars per share)	0.17	0.15
Dividends Per Share of Common Stock:
Dividends per share (in dollars per share)	$ 0.10	$ 0.10
Weighted average shares and share equivalents outstanding:
Weighted average shares and share equivalents outstanding, basic (in shares)	20,884	20,737
Weighted average shares and share equivalents outstanding, diluted (in shares)	21,837	21,245
Common Class B [Member]
Other income (expense):
Net income	$ 3,676	$ 3,287
Denominator for net income per share - basic:
Basic earnings per share (in dollars per share)	$ 1.04	$ 0.93
Numerator for net income per share - diluted:
Diluted earnings per share (in dollars per share)	1.01	0.91
Dividends Per Share of Common Stock:
Dividends per share (in dollars per share)	$ 0.60	$ 0.60
Weighted average shares and share equivalents outstanding:
Weighted average shares and share equivalents outstanding, basic (in shares)	3,527	3,513
Weighted average shares and share equivalents outstanding, diluted (in shares)	3,630	3,576