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Equity and Cash Incentive Program - Other Information Regarding Exercise of SARs and Stock Options (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Stock Appreciation Rights [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Fair value $ 1,239 $ 1,564 $ 1,356
Aggregate intrinsic value $ 2,787 $ 799 1,874
Stock Options [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Cash received from exercise of stock options     100
Aggregate intrinsic value     $ 117