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Stock-Based Compensation - Schedule of Information Related to Outstanding SOSARS (Detail) - Stock Only Stock Appreciation Rights (SOSARs) [Member] - $ / shares
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Beginning Balance, Outstanding 2,561,846 2,736,616
Exercised (138,423) (33,050)
Canceled / forfeited (20,994) (17,420)
Ending Balance, Outstanding 2,402,429 2,686,146
Beginning Balance, Weighted Average Exercise Price, Outstanding $ 17.87 $ 17.64
Weighted Average Exercise Price, Exercised 12.98 14.65
Weighted Average Exercise Price, Canceled / forfeited 18.76 18.38
Ending Balance, Weighted Average Exercise Price, Outstanding $ 18.14 $ 17.67