Stock-Based Compensation - Shares Issued in Connection with Stock Compensation Awards (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
New shares issued from available authorized shares	0	0	0	0
Issued from available treasury stock	71,284	19,232	225,184	447,831
Total	71,284	19,232	225,184	447,831
Proceeds from stock option exercises	$ 5,665	$ 1,119	$ 13,506	$ 26,567

Treasury Shares Issued Related To Stock Option Exercises

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Amount of cash inflow from exercise of stock options granted under share-based compensation arrangement.

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Number of share instruments newly issued under a share-based compensation plan.

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Number of shares issued during the period as a result of an employee stock purchase plan.

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