Revenue Recognition - Summarize Activity of the Net Product Revenue Allowance and Reserve Categories (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	$ 65,244	$ 48,093
Provision related to current period sales	94,995	45,860
Provision related to prior period sales		(704)
Credits/payments made for current period sales	(28,009)	(13,161)
Credits/payments made for prior period sales	(47,659)	(24,651)
Ending balance	84,571	55,437
Trade Allowances
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	19,495	12,035
Provision related to current period sales	15,881	8,506
Provision related to prior period sales		(200)
Credits/payments made for current period sales	(2,624)	(875)
Credits/payments made for prior period sales	(8,760)	(1,336)
Ending balance	23,992	18,130
Rebates, Chargebacks and Discounts
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	41,634	32,064
Provision related to current period sales	70,410	32,947
Provision related to prior period sales		(435)
Credits/payments made for current period sales	(18,494)	(10,487)
Credits/payments made for prior period sales	(37,521)	(20,994)
Ending balance	56,029	33,095
Product Returns
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	2,948	1,887
Provision related to current period sales	418	222
Credits/payments made for prior period sales	(179)	(25)
Ending balance	3,187	2,084
Other Incentives
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	1,167	2,107
Provision related to current period sales	8,286	4,185
Provision related to prior period sales		(69)
Credits/payments made for current period sales	(6,891)	(1,799)
Credits/payments made for prior period sales	(1,199)	(2,296)
Ending balance	$ 1,363	$ 2,128