Revenue Recognition - Summarize Activity of the Net Product Revenue Allowance and Reserve Categories (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	$ 65,244	$ 48,093
Provision related to current period sales	369,133	175,167
Provision related to prior period sales	(204)	(1,565)
Credits/payments made for current period sales	(249,600)	(106,961)
Credits/payments made for prior period sales	(62,540)	(43,617)
Ending balance	122,033	71,117
Trade Allowances
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	19,495	12,035
Provision related to current period sales	62,177	30,814
Provision related to prior period sales		(660)
Credits/payments made for current period sales	(34,400)	(15,908)
Credits/payments made for prior period sales	(19,325)	(11,657)
Ending balance	27,947	14,624
Rebates, Chargebacks and Discounts
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	41,634	32,064
Provision related to current period sales	274,439	128,905
Provision related to prior period sales	(204)	(836)
Credits/payments made for current period sales	(184,801)	(76,015)
Credits/payments made for prior period sales	(41,363)	(29,594)
Ending balance	89,705	54,524
Product Returns
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	2,948	1,887
Provision related to current period sales	1,635	812
Credits/payments made for current period sales	5
Credits/payments made for prior period sales	(653)	(69)
Ending balance	3,935	2,630
Other Incentives
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	1,167	2,107
Provision related to current period sales	30,882	14,636
Provision related to prior period sales		(69)
Credits/payments made for current period sales	(30,404)	(15,038)
Credits/payments made for prior period sales	(1,199)	(2,297)
Ending balance	$ 446	$ (661)