Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions	1 Months Ended
	Nov. 30, 2019	Mar. 31, 2019	Nov. 30, 2018	Jul. 31, 2017	Dec. 31, 2019	Dec. 31, 2018
Class Of Stock [Line Items]
Common stock issued	0.3
Common stock fair value					$ 8	$ 7
Common stock average price per share		$ 140.41	$ 131.00	$ 42.50
Net proceeds from issue of common stock		$ 365,400	$ 513,400	$ 354,000
Underwriting discounts, commission and offering expenses		$ 300	$ 24,600	$ 20,000
StrideBio, Inc. [Member]
Class Of Stock [Line Items]
Common stock fair value	$ 29,400
Underwritten Public Offering [Member]
Class Of Stock [Line Items]
Common stock issued		2.6	4.1	8.8
Underwritten Offering [Member]
Class Of Stock [Line Items]
Common stock issued			0.3	1.2