Product Revenue and Reserves for Variable Consideration - Summary of Product Revenue Allowance and Reserve Categories (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($)
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at December 31, 2018	$ 23,737
Current provisions related to sales in current year	19,832
Adjustments related to prior period sales	156
Credits/payments made relating to sales in current year	(5,229)
Credits/payments made relating to prior period sales	(14,514)
Balance at March 31, 2019	23,982
Chargebacks and Discounts
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at December 31, 2018	516
Current provisions related to sales in current year	1,486
Credits/payments made relating to sales in current year	(980)
Credits/payments made relating to prior period sales	(515)
Balance at March 31, 2019	507
Rebates, Fees and other Deductions
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at December 31, 2018	22,861
Current provisions related to sales in current year	17,476
Adjustments related to prior period sales	156
Credits/payments made relating to sales in current year	(4,249)
Credits/payments made relating to prior period sales	(13,052)
Balance at March 31, 2019	23,192
Returns
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at December 31, 2018	360
Current provisions related to sales in current year	870
Credits/payments made relating to prior period sales	(947)
Balance at March 31, 2019	$ 283