| Debt Outstanding (Detail) (USD $) In Millions, unless otherwise specified | Dec. 31, 2011 | Dec. 31, 2010 | Dec. 31, 2010
 Note, 4.25%, due in installments through May 2012 | Dec. 31, 2011
 Notes, 7.34%, due in installments through May 2014 | Dec. 31, 2010
 Notes, 7.34%, due in installments through May 2014 | May 31, 2007
 Notes, 7.34%, due in installments through May 2014 | Dec. 31, 2011
 Notes, 4.45%, due December 2014 | Dec. 31, 2010
 Notes, 4.45%, due December 2014 | Nov. 04, 2009
 Notes, 4.45%, due December 2014 | Dec. 31, 2011
 Notes, 6.30%, due July 2017 | Dec. 31, 2010
 Notes, 6.30%, due July 2017 | Jun. 28, 2007
 Notes, 6.30%, due July 2017 | Dec. 31, 2011
 Debentures, 6.90%, due July 2028 | Dec. 31, 2010
 Debentures, 6.90%, due July 2028 | Dec. 31, 2011
 Notes, 7.00%, due July 2037 | Dec. 31, 2010
 Notes, 7.00%, due July 2037 | Jun. 28, 2007
 Notes, 7.00%, due July 2037 | Dec. 31, 2011
 Commercial paper | Dec. 31, 2011
 Capitalized lease obligation | Dec. 31, 2010
 Capitalized lease obligation | Dec. 31, 2011
 Other | Dec. 31, 2010
 Other | 
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Debt Instrument [Line Items] | ||||||||||||||||||||||
| Total debt | $ 999.2 | $ 990.2 | $ 4.7 | $ 45.0 | $ 60.0 | $ 75.0 | $ 275.0 | $ 275.0 | $ 275.0 | $ 272.5 | $ 272.5 | $ 300.0 | $ 125.0 | $ 125.0 | $ 250.0 | $ 250.0 | $ 250.0 | $ 30.0 | $ 1.1 | $ 2.0 | $ 0.6 | $ 1.0 | 
| Less short-term debt and current maturities | (47.2) | (20.7) | ||||||||||||||||||||
| Less unamortized discounts | (1.8) | (2.1) | ||||||||||||||||||||
| Plus fair value adjustments | 15.8 | 11.5 | 1.0 | 14.8 | ||||||||||||||||||
| Total long-term debt, net of discount | $ 966.0 | $ 978.9 |