Significant Accounting Policies - Goodwill, Other Intangible and Long-Lived Assets (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Acquired Finite-Lived Intangible Assets [Line Items]
Impairments of intangible and long-lived assets	$ 1,400,000	$ 1,000,000
Impairment of long-lived assets	$ 1,430,000	$ 958,000	$ 716,000
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
Trademarks and tradenames | Minimum
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated useful life of definite-lived intangible asset	1 year
Trademarks and tradenames | 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