Debt and Financing (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
Debt [Line Items]
Total senior notes	$ 1,950.0		$ 1,950.0
Unaccreted discount	(1.4)		(1.4)
Short-term and Long-term debt, net of discount	1,948.6		1,948.6
Short-term debt	299.9		299.9			$ 0.0
Long-term debt	$ 1,648.7		$ 1,648.7			1,349.0
Redemption percent due to change in control	101.00%		101.00%
Financing Arrangements [Abstract]
Sale of receivable	$ 11.8	$ 209.8	$ 58.9	$ 342.7
Proceeds from sale and collection of receivables	25.5	$ 152.1	85.5	$ 344.4
Receivables from sale of receivables	1.4		$ 1.4			28.0
Maximum term for guarantees related to third-party financing arrangements			4 years
Cash received from financing provider that has not been recognized as revenue	13.3		$ 13.3			$ 67.5
Financing guarantee with recourse [Member]
Financing Arrangements [Abstract]
Guarantor obligations, current carrying value	11.2		$ 11.2
Minimum [Member]
Financing Arrangements [Abstract]
Number of days due from receivable			30 days
Maximum [Member]
Financing Arrangements [Abstract]
Number of days due from receivable			90 days
Fixed rate note due 2016 [Member]
Debt [Line Items]
Short-term debt, gross	$ 300.0		$ 300.0					$ 300.0
Effective interest rate	3.25%		3.25%
Long-term debt, stated interest rate	3.10%		3.10%					3.10%
Fixed rate note due 2020 [Member]
Debt [Line Items]
Long-term debt, gross	$ 300.0		$ 300.0		$ 300.0
Effective interest rate	3.47%		3.47%
Long-term debt, stated interest rate	3.30%		3.30%		3.30%
Redemption period			1 month
Fixed rate note due 2020 [Member] | One Month Prior to Maturity [Member]
Debt [Line Items]
Redemption price			100.00%
Fixed rate note due 2020 [Member] | Three Months Prior to Maturity [Member] | Treasury Rate [Member]
Debt [Line Items]
Redemption discount rate, basis spread on variable rate			0.30%
Fixed rate note due 2020 [Member] | On or After May 15, 2020 [Member]
Debt [Line Items]
Redemption price			100.00%
Fixed rate note due 2021 [Member]
Debt [Line Items]
Long-term debt, gross	$ 300.0		$ 300.0					$ 300.0
Effective interest rate	4.69%		4.69%
Long-term debt, stated interest rate	4.60%		4.60%					4.60%
Fixed rate note due 2024 [Member]
Debt [Line Items]
Long-term debt, gross	$ 350.0		$ 350.0				$ 350.0
Effective interest rate	4.63%		4.63%
Long-term debt, stated interest rate	4.50%		4.50%				4.50%
Fixed rate note due 2025 [Member]
Debt [Line Items]
Long-term debt, gross	$ 300.0		$ 300.0		$ 300.0
Effective interest rate	4.47%		4.47%
Long-term debt, stated interest rate	4.35%		4.35%		4.35%
Redemption period			3 months
Fixed rate note due 2025 [Member] | One Month Prior to Maturity [Member] | Treasury Rate [Member]
Debt [Line Items]
Redemption discount rate, basis spread on variable rate			0.375%
Fixed rate note due 2025 [Member] | Three Months Prior to Maturity [Member]
Debt [Line Items]
Redemption price			100.00%
Fixed rate note due 2025 [Member] | On or After March 15, 2025 [Member]
Debt [Line Items]
Redemption price			100.00%
Fixed rate note due 2041 [Member]
Debt [Line Items]
Long-term debt, gross	$ 400.0		$ 400.0					$ 400.0
Effective interest rate	6.03%		6.03%
Long-term debt, stated interest rate	5.95%		5.95%					5.95%
Other Fixed Rate Notes [Member]
Debt [Line Items]
Redemption price			100.00%