Operating Segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Summary of reportable segments
Revenue	$ 79,093	$ 73,450	$ 149,353	$ 139,192
Direct Margin	51,166	47,545	97,760	91,064
Selling, marketing, administrative and other expenses	(39,119)	(37,403)	(80,471)	(76,031)
Amortization of intangible assets	586	526	1,200	1,219
Income from operations	11,461	9,616	16,089	13,814
Business Technology [Member]
Summary of reportable segments
Revenue	40,559	37,830	80,215	74,285
Direct Margin	26,666	24,542	53,042	49,409
Marketing and Strategy [Member]
Summary of reportable segments
Revenue	30,186	28,928	60,035	56,210
Direct Margin	20,240	19,398	40,751	37,462
Events [Member]
Summary of reportable segments
Revenue	8,348	6,692	9,103	8,697
Direct Margin	$ 4,260	$ 3,605	$ 3,967	$ 4,193

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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The aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses. Direct selling expenses (for example, credit, warranty, and advertising) are expenses that can be directly linked to the sale of specific products. Indirect selling expenses are expenses that cannot be directly linked to the sale of specific products, for example telephone expenses, Internet, and postal charges. General and administrative expenses include salaries of non-sales personnel, rent, utilities, communication, etc.

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