Quarterly Results of Operations - Textual (Details) - USD ($)	3 Months Ended			12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition, Contingent Consideration [Line Items]
Earnings Per Share, Diluted, Pro Forma Adjustment		$ 0.14
Foreign exchange loss	$ (659)	$ (10,081)		$ (18,137,000)	$ 213,000	$ 39,328,000
Cost of services sold	7,480,000	5,560,000		24,350,000	21,003,000	17,796,000
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability				(4,819,000)	8,227,000	38,887,000
Asset Impairment Charges	4,415,000			4,415,000	48,524,000	0
Goodwill, Impairment Loss				3,238,000	48,524,000
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	(226,466,000)	925,000		232,632,000
Contingent Payment [Member]
Business Acquisition, Contingent Consideration [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	$ 18,173,000	9,211,000		4,896,000	7,972,000	$ 36,344,000
All Other [Domain]
Business Acquisition, Contingent Consideration [Line Items]
Goodwill, Impairment Loss				$ 3,238,000	$ 29,631,000
Strategic Communications [Member]
Business Acquisition, Contingent Consideration [Line Items]
Goodwill, Impairment Loss		$ 18,893,000
Experiential and Non-material [Member]
Business Acquisition, Contingent Consideration [Line Items]
Goodwill, Impairment Loss			$ 29,631,000