Summary of Change in Reserves for Discounts and Allowances (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Accounts Notes And Loans Receivable [Line Items]
Beginning balance	$ 51,503	$ 28,510
Provision	78,439	68,987
Payments/credits	(78,972)	(45,994)
Ending balance	50,970	51,503
Chargebacks [Member]
Accounts Notes And Loans Receivable [Line Items]
Beginning balance	588	1,378
Provision	9,700	9,698
Payments/credits	(8,007)	(10,488)
Ending balance	2,281	588
Rebates [Member]
Accounts Notes And Loans Receivable [Line Items]
Beginning balance	44,738	24,276
Provision	52,180	44,749
Payments/credits	(55,147)	(24,287)
Ending balance	41,771	44,738
Prompt Pay [Member]
Accounts Notes And Loans Receivable [Line Items]
Beginning balance	1,506	538
Provision	6,384	4,897
Payments/credits	(5,941)	(3,929)
Ending balance	1,949	1,506
Other Accruals [Member]
Accounts Notes And Loans Receivable [Line Items]
Beginning balance	4,671	2,318
Provision	10,175	9,643
Payments/credits	(9,877)	(7,290)
Ending balance	$ 4,969	$ 4,671