Share-Based Compensation - Summary of Activity Under Share-Based Compensation Plans (Parenthetical) (Detail) - shares shares in Millions  | 
Dec. 31, 2015  | 
Dec. 31, 2014  | 
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| Market condition awards [Member] | ||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||
| Outstanding SARs | 0.1 | 1.5 | 
| Performance condition SARs [Member] | ||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||
| Outstanding SARs | 2.5 | 1.0 | 
| Exercisable SARs | 0.3 | 
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- Definition The number of exercisable stock appreciation rights (SARs). No definition available. 
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- Definition The number of outstanding stock appreciation rights (SARs). No definition available. 
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available. 
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