Long-term Debt (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	Dec. 31, 2013
Debt Instrument
Early Repayment of Senior Debt				$ 371.2
Discount				350.1		1.2
Long-term Debt	1,632.3			1,632.3			1,483.4
Less: current portion	2.4	[1]		2.4	[1]		353.6	[1]
Long-term Debt, Excluding Current Maturities	1,629.9			1,629.9			1,129.8
Loss on Early Extinguishment of Debt	(10.4)		0	(10.4)		0
Proceeds from Issuance of Long-term Debt				499.1		0
6.25% Notes
Debt Instrument
Debt Instrument, Interest Rate, Effective Percentage	6.29%			6.29%
Debt Instrument, Interest Rate, Stated Percentage	6.25%			6.25%
Interest Paid, Net				10.3
Debt Instrument, Face Amount	350.0			350.0
Debt Instrument, Maturity Date				Nov. 15, 2014
Debt Instrument, Unamortized Discount	0			0
Long-term Debt, Gross	0			0			351.3
Long-term Debt, Fair Value	0	[2]		0	[2]		365.6	[2]
2.25% Notes
Debt Instrument
Debt Instrument, Interest Rate, Effective Percentage	2.30%			2.30%
Debt Instrument, Interest Rate, Stated Percentage	2.25%			2.25%
Debt Instrument, Maturity Date				Nov. 15, 2017
Debt Instrument, Unamortized Discount	0.5			0.5
Long-term Debt, Gross	299.5			299.5			299.4
Long-term Debt, Fair Value	304.7	[2]		304.7	[2]		293.0	[2]
4.00% Notes
Debt Instrument
Debt Instrument, Interest Rate, Effective Percentage	4.13%			4.13%
Debt Instrument, Interest Rate, Stated Percentage	4.00%			4.00%
Debt Instrument, Maturity Date				Mar. 15, 2022
Debt Instrument, Unamortized Discount	2.4			2.4
Long-term Debt, Gross	247.6			247.6			247.4
Long-term Debt, Fair Value	256.9	[2]		256.9	[2]		241.6	[2]
3.75% Notes
Debt Instrument
Debt Instrument, Interest Rate, Effective Percentage	4.32%			4.32%
Debt Instrument, Interest Rate, Stated Percentage	3.75%			3.75%
Debt Instrument, Maturity Date				Feb. 15, 2023
Debt Instrument, Unamortized Discount	1.3			1.3
Long-term Debt, Gross	498.7			498.7			498.6
Long-term Debt, Fair Value	501.8	[2]		501.8	[2]		467.3	[2]
4.20% Notes
Debt Instrument
Debt Instrument, Interest Rate, Effective Percentage	4.24%			4.24%
Debt Instrument, Interest Rate, Stated Percentage	4.20%			4.20%
Discount				0.9
Debt Instrument, Face Amount	500.0			500.0
Debt Instrument, Maturity Date				Apr. 15, 2024
Debt Instrument, Unamortized Discount	0.9			0.9
Fees and Commissions				4.4
Long-term Debt, Gross	499.1			499.1			0
Long-term Debt, Fair Value	514.4	[2]		514.4	[2]		0	[2]
Proceeds from Issuance of Long-term Debt				494.7
Debt Instrument, Frequency of Periodic Payment				semi-annually
Other notes payable and capitalized leases
Debt Instrument
Long-term Debt, Gross	87.4			87.4			86.7
Long-term Debt, Fair Value	$ 89.4	[2]		$ 89.4	[2]		$ 87.8	[2]

[1] We included our 6.25% Senior Unsecured Notes due 2014 (the "6.25% Notes") in the current portion of long-term debt on our December 31, 2013 Consolidated Balance Sheet because the 6.25% Notes were scheduled to mature on November 15, 2014. We redeemed the 6.25% Notes prior to their scheduled maturity during the second quarter of 2014.

[2] See Note 12 for information on the fair value measurement of our long-term debt.