Quarterly Results of Operations - Textual (Details) - USD ($)	3 Months Ended			12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition, Contingent Consideration [Line Items]
Earnings Per Share, Diluted, Pro Forma Adjustment	$ 0.14
Foreign exchange loss	$ (10,081)		$ (9,531)	$ 213,000	$ 39,328,000	$ 18,482,000
Cost of services sold	5,560		4,771	21,003,000	17,796,000	17,696,000
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability				8,227,000	38,887,000	18,652,000
Goodwill, Impairment Loss				48,524,000	0	0
Contingent Payment [Member]
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	(9,211)		$ 41,913	7,972,000	$ 36,344,000	$ 16,467,000
All Other [Domain]
Business Acquisition, Contingent Consideration [Line Items]
Goodwill, Impairment Loss				$ 29,631,000
Strategic Communications [Member]
Business Acquisition, Contingent Consideration [Line Items]
Goodwill, Impairment Loss	$ 18,893
Experiential and Non-material [Member]
Business Acquisition, Contingent Consideration [Line Items]
Goodwill, Impairment Loss		$ 30,000