Financing Arrangements - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	May 07, 2012 Issuance of Notes payable
Line of Credit Facility [Line Items]
Credit facility maximum borrowing capacity	$ 1,500,000,000
Credit facility, maturity date	2016-06
Credit facility Interest rate above LIBOR	1.50%
Current maturities of long-term debt	350,034,000	350,005,000
Notes payable, maturity date	May 01, 2012
Notes payable, maturity period	10 years
New Notes payable to be issued			$ 500,000,000