Summary of Significant Accounting Policies - Summary of Changes in Reserves for Product Returns and Sales Allowances (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Rebates and Chargebacks [Member]
Revenue From Contract With Customer Contractual Adjustments [Line Items]
Balance at beginning of year	$ 2,694	$ 1,315
Accruals and adjustments	15,383	9,586
Payments and other reserve reductions	(11,769)	(8,207)
Balance at end of year	6,308	2,694
Patient Discount Programs [Member]
Revenue From Contract With Customer Contractual Adjustments [Line Items]
Balance at beginning of year	1,290	115
Accruals and adjustments	6,716	2,429
Payments and other reserve reductions	(7,161)	(1,254)
Balance at end of year	845	1,290
Returns [Member]
Revenue From Contract With Customer Contractual Adjustments [Line Items]
Balance at beginning of year	1,153	245
Accruals and adjustments	2,520	1,628
Payments and other reserve reductions	(3,303)	(720)
Balance at end of year	370	1,153
Wholesaler Distribution Fees [Member]
Revenue From Contract With Customer Contractual Adjustments [Line Items]
Balance at beginning of year	790	465
Accruals and adjustments	6,393	3,519
Payments and other reserve reductions	(5,500)	(3,194)
Balance at end of year	1,683	790
Prompt Payment Discounts [Member]
Revenue From Contract With Customer Contractual Adjustments [Line Items]
Balance at beginning of year	216	84
Accruals and adjustments	1,491	742
Payments and other reserve reductions	(1,387)	(610)
Balance at end of year	$ 320	$ 216