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Stock and Incentive Programs for Employees and Directors - Performance Share Units - Narrative (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Share-based compensation $ 17.3 $ 17.7 $ 19.9
Unrecognized share-based compensation cost $ 19.3    
Unrecognized compensation expense, weighted-average period of recognition 1 year 9 months 18 days    
Performance share units      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Performance share unit awards granted to certain executive officers 418,000 319,000 485,000
Equity instruments other than options, payout range, minimum 209,000 154,500  
Equity instruments other than options, payout range, maximum 627,000 319,000 485,000
Equity instruments other than options vested in period 485,000   485,000
Equity instruments other than options, percentage of expected payout 100.00% 100.00% 100.00%
Share-based compensation $ 5.1 $ 3.5 $ 2.5
Unrecognized share-based compensation cost $ 6.7    
Unrecognized compensation expense, weighted-average period of recognition 1 year 8 months 12 days