Stock-Based Compensation - Shares Issued in Connection with Stock Compensation Awards (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-based Payment Arrangement [Abstract]
New shares issued from available authorized shares	0	0	0	0
Issued from available treasury stock	53,425	71,284	196,948	225,184
Total	53,425	71,284	196,948	225,184
Proceeds from stock option exercises	$ 2,698	$ 5,665	$ 7,544	$ 13,506

Treasury Shares Issued Related To Stock Option Exercises

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Amount of cash inflow from exercise of option under share-based payment arrangement.

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Number of shares issued under share-based payment arrangement.

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

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