Shareholders' Equity - Summary of Activities in Common Stock (Detail) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Equity [Abstract]
Purchases of treasury (in shares)	0	0	(72)	0
Stock option exercises (in shares)	395	326	691	1,048
Employee stock plan purchases (in shares)	15	12	43	35
Restricted stock units vested, net of withheld shares upon award settlement (in shares)	1	0	38	0
Purchases of treasury shares	$ 0	$ 0	$ (14,289)	$ 0
Stock option exercises	40,163	26,219	62,295	70,536
Employee stock plan purchases	2,718	2,218	7,327	5,978
Restricted stock units vested, net of withheld shares upon award settlement	$ (191)	$ 0	$ (3,572)	$ 0