Significant Accounting Policies - Goodwill, Other Intangible and Long-Lived Assets (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Acquired Finite-Lived Intangible Assets [Line Items]
Impairment of Intangible Assets, Finite-lived	$ 0.2	$ 1.4
Customer and advertiser relationships | Minimum
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated useful life of definite-lived intangible asset	6 years
Customer and advertiser relationships | Maximum
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated useful life of definite-lived intangible asset	10 years
Developed technology and patents | Minimum
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated useful life of definite-lived intangible asset	5 years
Developed technology and patents | Maximum
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated useful life of definite-lived intangible asset	20 years
Media content
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated useful life of definite-lived intangible asset	5 years
Trademarks and trade names | Minimum
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated useful life of definite-lived intangible asset	1 year
Trademarks and trade names | Maximum
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated useful life of definite-lived intangible asset	3 years
Service contracts and other
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated useful life of definite-lived intangible asset	10 years