Commitments and Contingencies (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Mar. 31, 2011
Summarization of principal contractual obligations
Future minimum payments under the non-cancelable operating leases	$ 118.6		$ 118.6
Rent expense	10.9	$ 12.7	22.4	$ 25.7
Total purchase commitments	476.4		476.4
Accrual for estimated carrying charges or obsolete materials charges	20.6		20.6
Short-term debt	299.9		299.9			$ 0.0
Long-term debt, carrying value	1,648.7		1,648.7			1,349.0
Indemnity-related and service-related escrows	45.7		45.7
Campus build out commitments	3.5		3.5
Other contractual obligations	26.0		26.0
Long-term income taxes payable	180.2		180.2			$ 177.5
Fixed rate note due 2016 [Member]
Summarization of principal contractual obligations
Short-term debt, gross	$ 300.0		$ 300.0					$ 300.0
Short-term and Long-term debt, stated interest rate	3.10%		3.10%					3.10%
Fixed rate note due 2020 [Member]
Summarization of principal contractual obligations
Long-term debt, gross	$ 300.0		$ 300.0		$ 300.0
Short-term and Long-term debt, stated interest rate	3.30%		3.30%		3.30%
Fixed rate note due 2021 [Member]
Summarization of principal contractual obligations
Long-term debt, gross	$ 300.0		$ 300.0					$ 300.0
Short-term and Long-term debt, stated interest rate	4.60%		4.60%					4.60%
Fixed rate note due 2024 [Member]
Summarization of principal contractual obligations
Long-term debt, gross	$ 350.0		$ 350.0				$ 350.0
Short-term and Long-term debt, stated interest rate	4.50%		4.50%				4.50%
Fixed rate note due 2025 [Member]
Summarization of principal contractual obligations
Long-term debt, gross	$ 300.0		$ 300.0		$ 300.0
Short-term and Long-term debt, stated interest rate	4.35%		4.35%		4.35%
Fixed rate note due 2041 [Member]
Summarization of principal contractual obligations
Long-term debt, gross	$ 400.0		$ 400.0					$ 400.0
Short-term and Long-term debt, stated interest rate	5.95%		5.95%					5.95%