Accounts Receivable (Narrative) (Detail) (USD $)	9 Months Ended
	Sep. 30, 2012		Feb. 06, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Trade accounts receivable securitization facility	$ 500,000,000
Maximum undivided ownership interest pooled accounts receivable amount sold	500,000,000
Deferred financing fees			600,000
Securitization facility	$ 355,000,000	[1]		$ 280,000,000	[1]

[1] The Company is party to a receivables purchase agreement (Securitization Facility) that was amended and restated for the fourth time as of October 29, 2007 and which has been amended seven times since then to add or remove purchasers, extend the facility termination date and remove all financial covenants. The current purchase limit under the Securitization Facility is $500 million. The Securitization Facility was amended for the seventh time on February 6, 2012 to add a new purchaser and extend the facility termination date to February 4, 2013. There is a program fee equal to the Commercial Paper Rate of 0.27%, plus 0.75% as of September 30, 2012. The unused facility fee is payable at a rate of 0.35% per annum as of September 30, 2012. The Securitization Facility provides for certain termination events, which includes nonpayment, upon the occurrence of which the administrator may declare the facility termination date to have occurred, may exercise certain enforcement rights with respect to the receivables, and may appoint a successor servicer, among other things.