Stock-Based Compensation - Shares Issued in Connection with Stock Compensation Awards (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
New shares issued from available authorized shares	310,021	0	593,363	0
Issued from available treasury stock	0	65,200	158,712	67,075
Total	310,021	65,200	752,075	67,075
Proceeds from stock option exercises	$ 19,402	$ 3,490	$ 44,149	$ 3,586