Fair Value Measurements (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Changes in the fair values of the entity's Level 3 assets and liabilities
Marketable equity securities, cost basis	$ 1,200,000
Impairment charge	900,000
Reconciliation of changes in the fair values of level 3 liabilities
Fair value of debt based on average trading price	452,200,000
Earnouts
Reconciliation of changes in the fair values of level 3 liabilities
Balance at the beginning of period	1,673,000	1,602,000
Additions	1,855,000	939,000	2,602,000
Payments			(1,000,000)
Change in fair value recognized in earnings	(671,000)	(868,000)
Balance at the end of period	2,857,000	1,673,000	1,602,000
Springbox Revenue Sharing
Changes in the fair values of the entity's Level 3 assets and liabilities
Period after the date of sale entity entitled to receive a percentage of revenue collected	3 years
Changes in fair value of Level 3 assets
Additions	768,000
Balance at the end of the period	768,000
EyeWonder Contingent Consideration
Changes in the fair values of the entity's Level 3 assets and liabilities
Amount held back from purchase price for certain transaction costs		$ 5,000,000
Period for which amount is held back to fund transaction costs		1 year