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Long-Term Incentive Plans - Summary of Activity in Outstanding Grants (Detail)
12 Months Ended
Dec. 31, 2015
shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]  
Outstanding grants at beginning of period (in shares) 115,300.0
Grants during the period (in shares) 51,900.0
Grants vested and paid during the period (in shares) (29,000)
Forfeitures during the period (in shares) (12,000)
Outstanding grants at the end of the period (in shares) 126,000