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Stock-based Compensation Plans - Stock Option and SARs Activities (Detail) - Stock Appreciation Rights (SARs)
3 Months Ended
Mar. 31, 2018
$ / shares
shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]  
Beginning Balance, Shares | shares 382,779
Expired/forfeited, Shares | shares (45,572)
Ending Balance, Shares | shares 337,207
Beginning Balance, Weighted Average Exercise Price | $ / shares $ 76.54
Expired/forfeited, Weighted Average Exercise Price | $ / shares 71.03
Ending Balance, Weighted Average Exercise Price | $ / shares $ 77.28