Stock-Based Compensation - Shares Issued in Connection with Stock Compensation Awards (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
New shares issued from available authorized shares	9,299	0	602,662	0
Issued from available treasury stock	13,425	841,846	172,137	908,921
Total	22,724	841,846	774,799	908,921
Proceeds from stock option exercises	$ 1,274	$ 44,287	$ 45,422	$ 47,873