Quarterly report pursuant to Section 13 or 15(d)

Fair Value of Employee Stock Options Granted as Determined by Black-Scholes Valuation Model Assumptions (Detail)

v2.4.0.6
Fair Value of Employee Stock Options Granted as Determined by Black-Scholes Valuation Model Assumptions (Detail) (Nonqualified Stock Options [Member])
3 Months Ended
Jun. 30, 2011
Y
Nonqualified Stock Options [Member]
 
Stockholders Equity Note [Line Items]  
Expected life (in years) 7.5
Risk-free interest rate 1.63%
Expected volatility 25.06%
Expected dividend yield 2.77%