Stock-Based Compensation - Shares Issued in Connection with Stock Compensation Awards (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 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	53,035	110,489	153,900	428,599
Total	53,035	110,489	153,900	428,599
Proceeds from stock option exercises	$ 2,956	$ 6,283	$ 7,841	$ 25,448

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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