Weighted Average Assumptions used in Black-Scholes Option Valuation Model for Stock Options Granted (Parenthetical) (Detail) (2006 Equity Incentive Plan, Chief Executive Officer)	1 Months Ended
	Mar. 31, 2012
2006 Equity Incentive Plan | Chief Executive Officer
Share based Compensation Arrangement by Share based Payment Award, Fair Value Assumptions, Method Used [Line Items]
Stock options granted that are subject to performance condition	100,000