Acquisitions (Estimated Fair Values of Assets Acquired and Liabilities Assumed) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Estimated useful lives of intangible assets	6 years 3 months 15 days	6 years 2 months 12 days
Podio [Member]
Current assets	1,906
Other assets	33
Property and equipment	0
Deferred tax assets, non-current	0
Intangible assets	24,600
Goodwill	25,473
Assets acquired	52,012
Current liabilities assumed	(609)
Long-term liabilities assumed	0
Deferred tax liabilities, non-current	(6,150)
Net assets acquired	45,253
Bytemobile [Member]
Current assets	58,849
Other assets	7,406
Property and equipment	2,484
Deferred tax assets, non-current	39,976
Intangible assets	248,900
Goodwill	225,344
Assets acquired	582,959
Current liabilities assumed	(57,569)
Long-term liabilities assumed	(4,487)
Deferred tax liabilities, non-current	(115,768)
Net assets acquired	405,135
Acquisition 2012 [Member]
Current assets	2,585
Other assets	75
Property and equipment	209
Deferred tax assets, non-current	11,752
Intangible assets	29,002
Goodwill	33,042
Assets acquired	76,665
Current liabilities assumed	(7,494)
Long-term liabilities assumed	(7,760)
Deferred tax liabilities, non-current	(11,039)
Net assets acquired	50,372
Minimum [Member]
Estimated useful lives of intangible assets	3 years
Minimum [Member] | Podio [Member]
Estimated useful lives of intangible assets	4 years
Minimum [Member] | Bytemobile [Member]
Estimated useful lives of intangible assets	1 year
Minimum [Member] | Acquisition 2012 [Member]
Estimated useful lives of intangible assets	3 years
Maximum [Member]
Estimated useful lives of intangible assets	7 years
Maximum [Member] | Podio [Member]
Estimated useful lives of intangible assets	5 years
Maximum [Member] | Bytemobile [Member]
Estimated useful lives of intangible assets	9 years
Maximum [Member] | Acquisition 2012 [Member]
Estimated useful lives of intangible assets	5 years