Financial Assets and Liabilities Accounted for at Fair Value on a Recurring Basis (Detail) (Fair Value, Measurements, Recurring, USD $) In Millions	Jun. 30, 2011		Dec. 31, 2010
Assets:
Money market mutual funds	$ 589.5	[1]	$ 681.2	[1]
Interest rate swaps	11.1	[2]	9.6	[2]
Assets, Fair Value Disclosure, Total	600.6		690.8
Liabilities:
Interest rate swaps			0.3	[2]
Commodity purchase contracts	1.3	[3]	2.2	[3]
Liabilities, Fair Value Disclosure, Total			2.5
Level 1
Assets:
Money market mutual funds	589.5	[1]	681.2	[1]
Assets, Fair Value Disclosure, Total	589.5		681.2
Level 2
Assets:
Interest rate swaps	11.1	[2]	9.6	[2]
Assets, Fair Value Disclosure, Total	11.1		9.6
Liabilities:
Interest rate swaps			0.3	[2]
Commodity purchase contracts	1.3	[3]	2.2	[3]
Liabilities, Fair Value Disclosure, Total			$ 2.5

[1] The fair value of money market mutual funds is based on quoted prices reported on various U.S. and international stock exchanges.

[2] The fair value of interest rate swaps is calculated using models that discount the cash flows at each coupon adjustment date using the then-applicable forward interest rates.

[3] The fair value of commodity purchase contracts is based on market forward rates and reflects the present value of the amount that the company would pay or receive for contracts involving the same notional amounts and maturity dates.