Assumptions Used to Determine Compensation Cost for the Company's Non-Qualified Stock Options Issued (Detail) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010		Dec. 31, 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value per share	$ 8.86	$ 9.06	[1]	$ 7.31
Expected dividend yield	0.55%	0.58%	[1]	0.60%
Risk-free interest rate	2.35%	2.55%	[1]	2.14%
Expected volatility	24.00%	22.00%	[1]	22.00%
Expected life (years)	5.07	6.42	[1]	4.84

[1] In 2010, the Human Resources Committee of the Company’s Board of Directors reviewed the Company’s practices for NQSO grants and determined that it would be more appropriate to make all regular equity grants in the February time frame, after the Company’s financial results are known for the prior year. Accordingly, there were no grants of NQSO in December 2010, which had been the historic practice.