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Employee Compensation Plans - Schedule of Fair Value of Awarded Stock Option Estimated on Grant Date Using Black-Scholes Option- Pricing Model (Detail) (USD $)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Dec. 31, 2008
Dec. 31, 2007
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Expected term 5 years 5 years 4 years 6 months 5 years 2 years 4 months 24 days 5 years
Expected volatility factor 54.95% 52.52% 48.58% 39.17% 36.41% 39.67%
Risk-free interest rate 0.70% 2.00% 2.62% 3.32% 2.13% 4.54%
Actual dividends $ 0.44 $ 0.44 $ 0.44 $ 0.44 $ 0.44 $ 0.40