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Share-Based Compensation Plans - Black-Scholes Option-Pricing Model (Detail)
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12 Months Ended | |
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Dec. 31, 2012
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Dec. 31, 2011
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| Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions And Methodology [Abstract] | ||
| Expected Term (years) | 3 years | 3 years |
| Risk-Free Interest Rate | 0.39% | 0.71% |
| Expected Dividend Yield | 8.21% | 7.31% |
| Expected Volatility | 21.12% | 33.58% |
| Forfeiture Rate | 1.00% | 2.00% |