Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenue	$ 98,837us-gaap_Revenues	$ 92,590us-gaap_Revenues	$ 86,421us-gaap_Revenues
Operating expenses:
Direct	41,719us-gaap_DirectOperatingCosts	38,844us-gaap_DirectOperatingCosts	35,461us-gaap_DirectOperatingCosts
Selling, general and administrative	25,018	25,208	23,542
Depreciation and amortization	3,804	3,732	4,699
Total operating expenses	70,541us-gaap_OperatingExpenses	67,784us-gaap_OperatingExpenses	63,702us-gaap_OperatingExpenses
Operating income	28,296us-gaap_OperatingIncomeLoss	24,806us-gaap_OperatingIncomeLoss	22,719us-gaap_OperatingIncomeLoss
Other income (expense):
Interest income	83us-gaap_InvestmentIncomeInterest	63us-gaap_InvestmentIncomeInterest	32us-gaap_InvestmentIncomeInterest
Interest expense	(305)us-gaap_InterestExpense	(397)us-gaap_InterestExpense	(541)us-gaap_InterestExpense
Other, net	18us-gaap_OtherNonoperatingIncomeExpense	16us-gaap_OtherNonoperatingIncomeExpense	(3)us-gaap_OtherNonoperatingIncomeExpense
Total other expense	(204)us-gaap_NonoperatingIncomeExpense	(318)us-gaap_NonoperatingIncomeExpense	(512)us-gaap_NonoperatingIncomeExpense
Income before income taxes	28,092	24,488	22,207
Provision for income taxes	9,936us-gaap_IncomeTaxExpenseBenefit	9,004us-gaap_IncomeTaxExpenseBenefit	7,139us-gaap_IncomeTaxExpenseBenefit
Net income	18,156us-gaap_NetIncomeLoss	15,484us-gaap_NetIncomeLoss	15,068us-gaap_NetIncomeLoss
Common Class A [Member]
Other income (expense):
Net income	9,062	7,741	7,534
Earnings per share of common stock:
Earnings per share, Basic (in Dollars per share)	$ 0.44	$ 0.37	$ 0.37
Diluted earnings per share:
Earnings per share, Diluted (in Dollars per share)	$ 0.43	$ 0.37	$ 0.36
Weighted average shares and share equivalents outstanding
Weighted average shares and share equivalents outstanding, basic (in Shares)	20,764	20,677	20,325
Weighted average shares and share equivalents outstanding, diluted (in Shares)	21,076	21,099	20,854
Common Class B [Member]
Other income (expense):
Net income	$ 9,094	$ 7,743	$ 7,534
Earnings per share of common stock:
Earnings per share, Basic (in Dollars per share)	$ 2.62	$ 2.25	$ 2.22
Diluted earnings per share:
Earnings per share, Diluted (in Dollars per share)	$ 2.57	$ 2.20	$ 2.17
Weighted average shares and share equivalents outstanding
Weighted average shares and share equivalents outstanding, basic (in Shares)	3,473	3,447	3,388
Weighted average shares and share equivalents outstanding, diluted (in Shares)	3,536	3,514	3,476

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