Employee Incentive and Retirement Plans - Black-Scholes Option Pricing Model to Estimate Fair Value of Stock Options Granted (Detail) |
3 Months Ended | 6 Months Ended | ||
---|---|---|---|---|
Jun. 30, 2015 |
Jun. 30, 2014 |
Jun. 30, 2015 |
Jun. 30, 2014 |
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Disclosure of Compensation Related Costs, Share-based Payments [Abstract] | ||||
Expected dividend yield | 0.00% | 0.00% | 0.00% | 0.00% |
Weighted-average assumed stock price volatility | 48.30% | 52.40% | 49.40% | 54.30% |
Weighted-average risk-free rate | 1.72% | 1.94% | 1.61% | 1.91% |
Weighted-average expected life (in years) | 6 years 3 months | 6 years 3 months 5 days | 6 years 3 months | 6 years 4 months 15 days |