Shareholders' Equity - Summary of Activities in Common Stock (Detail) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Equity [Abstract]
Stock option exercises, Shares	999	1,126	1,113
Purchases of common stock, Shares	(72)	(781)	(44)
Employee stock plan purchases, Shares	53	45	51
Restricted stock units vested, net of withheld shares upon award settlement, Shares	53	0	0
Issuance of shares pursuant to stock compensation plan	$ 96,908	$ 74,907	$ 49,845
Purchases of common stock	(14,289)	(150,050)	(6,613)
Employee stock plan purchases	9,576	8,051	7,044
Restricted stock units vested, net of withheld shares upon award settlement	$ (5,361)	$ 0	$ 0