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Stock-Based Compensation - Schedule of Summarized Activity of Stock Appreciation (Detail) - Stock Appreciation Rights
$ / shares in Units, shares in Thousands, $ in Millions
12 Months Ended
Dec. 31, 2020
USD ($)
$ / shares
shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]  
Outstanding at beginning of period (shares) 55
Granted (shares) 0
Exercised (shares) (15)
Cancelled/expired/forfeited (shares) 0
Outstanding at end of period (shares) 40
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]  
Outstanding at beginning of period (USD per share) | $ / shares $ 23.39
Exercised (USD per share) | $ / shares 21.69
Outstanding at end of period (USD per share) | $ / shares $ 24.04
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]  
Outstanding at end of period, weighted-average remaining contractual term (in years) 2 years 10 months 24 days
Outstanding at end of period, aggregate intrinsic value | $ $ 1.4
Exercisable at end of period, Number of options (shares) 40
Exercisable at end of period, weighted-average exercise price (USD per share) | $ / shares $ 24.04
Exercisable at end of period, weighted-average remaining contractual term 2 years 10 months 24 days
Exercisable at end of period, aggregate intrinsic value | $ $ 1.4