Assumptions Used in Estimating the Grant Date Fair Value of Options Using the Black-Scholes Option Pricing Model (Detail)	9 Months Ended
Sep. 30, 2011 contracts years	Sep. 30, 2010 years
Dividend yield	0.75%	0.17%
Expected stock price volatility	34.87%	56.09%
Risk-free interest rate (weighted average)	2.48%	2.80%
Expected life of options	6	6

The period of time an equity-based award is expected to be outstanding. An equity-based award's expected term is generally determined based on, among other factors, the instrument's contractual term and the effects of employees' expected exercise and post-vesting employment termination behavior.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 14

-Section D

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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