Shareholders' Equity - Summary of Activities in Common Stock (Detail) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Equity [Abstract]
Purchases of treasury shares	$ (2)	$ 0	$ (15,484)	$ (14,289)
Purchases of treasury (in shares)	0	0	(59)	(72)
Stock option exercises	$ 8,395	$ 40,163	$ 100,732	$ 62,295
Stock option exercises (in shares)	72	395	989	691
Employee stock plan purchases	$ 3,032	$ 2,718	$ 8,209	$ 7,327
Employee stock plan purchases (in shares)	11	15	31	43
Restricted stock units vested, net of withheld shares upon award settlement	$ (316)	$ (191)	$ (7,208)	$ (3,572)
Restricted stock units vested, net of withheld shares upon award settlement (in shares)	2	1	45	38