Acquisitions (Details Textual) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Oct. 01, 2015	May. 01, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Adjustments to deferred acquisition consideration included in share-based compensation	$ 2,906	$ 2,668
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests	0		$ 155,042,000
Redeemable Noncontrolling Interest, Equity, Fair Value	$ 71,000,000		69,471,000			$ 194,951,000
Noncontrolling Interest, Ownership Percentage by Parent	100.00%
Aggregate 2015 Acquisitions [Member]
Business Acquisition [Line Items]
Business Acquisition, Cost of Acquired Entity, Cash Paid			23,000
Business Combination, Consideration Transferred, Liabilities Incurred			32,279
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles			16,721
Goodwill, Acquired During Period			$ 43,654
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			6 years 4 months
Business Acquisition, Goodwill, Expected Tax Deductible Amount			$ 9,720
Business Combination, Consideration Transferred			55,279
Aggregate 2015 Acquisitions [Member] | Y Media Labs, LLC [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value			1,999
Business Acquisition, Percentage of Voting Interests Acquired					60.00%
Aggregate 2015 Acquisitions [Member] | Unique Influence, LLC [Domain]
Business Acquisition [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired				100.00%
Aggregate 2015 Step Up Transactions [Member]
Business Acquisition [Line Items]
Business Acquisition, Cost of Acquired Entity, Cash Paid			37,467
Business Combination, Consideration Transferred, Liabilities Incurred			163,355
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests			149,335
Business Combination, Consideration Transferred			200,822
Noncontrolling Interest [Member] | Aggregate 2015 Step Up Transactions [Member]
Business Acquisition [Line Items]
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests			8,708
Additional Paid-in Capital [Member] | Aggregate 2015 Step Up Transactions [Member]
Business Acquisition [Line Items]
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests			$ 42,780
Contingent payment [Domain]
Business Acquisition [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	$ 6,327,000	$ 2,248,000