Summary of Change in Reserves for Discounts and Allowances (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Accounts Notes And Loans Receivable [Line Items]
Beginning balance	$ 50,970	$ 51,503
Provision	80,871	58,545
Payments/credits	64,156	(58,230)
Ending balance	67,685	51,818
Chargebacks [Member]
Accounts Notes And Loans Receivable [Line Items]
Beginning balance	2,281	588
Provision	9,350	7,137
Payments/credits	10,878	6,699
Ending balance	753	1,026
Rebates [Member]
Accounts Notes And Loans Receivable [Line Items]
Beginning balance	41,771	44,738
Provision	54,686	38,763
Payments/credits	37,818	39,489
Ending balance	58,639	44,012
Prompt Pay [Member]
Accounts Notes And Loans Receivable [Line Items]
Beginning balance	1,949	1,506
Provision	6,603	4,599
Payments/credits	5,865	4,348
Ending balance	2,687	1,757
Other Accruals [Member]
Accounts Notes And Loans Receivable [Line Items]
Beginning balance	4,969	4,671
Provision	10,232	8,046
Payments/credits	9,595	7,694
Ending balance	$ 5,606	$ 5,023