Goodwill and Purchased Intangible Assets, Finite Lived Intangible Assets by Class (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 9.8	$ 7.7	$ 19.3	$ 15.2
Cost of Revenues [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	8.4	6.5	16.6	12.8
Sales and Marketing Expense [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	1.1	0.9	2.1	1.8
General and Administrative Expense [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	0.3	0.3	0.6	0.6
Operating expense [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 1.4	$ 1.2	$ 2.7	$ 2.4