Summary of Change in Reserves for Discounts and Allowances (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Accounts Notes And Loans Receivable [Line Items]
Beginning balance	$ 50,970	$ 51,503
Provision	49,739	37,445
Payments/credits	(44,648)	(40,559)
Ending balance	56,061	48,389
Chargebacks [Member]
Accounts Notes And Loans Receivable [Line Items]
Beginning balance	2,281	588
Provision	5,665	4,480
Payments/credits	(6,887)	(4,427)
Ending balance	1,059	641
Rebates [Member]
Accounts Notes And Loans Receivable [Line Items]
Beginning balance	41,771	44,738
Provision	33,221	25,664
Payments/credits	(26,992)	(27,617)
Ending balance	48,000	42,785
Prompt Pay [Member]
Accounts Notes And Loans Receivable [Line Items]
Beginning balance	1,949	1,506
Provision	4,005	2,952
Payments/credits	(3,533)	(2,796)
Ending balance	2,421	1,662
Other Accruals [Member]
Accounts Notes And Loans Receivable [Line Items]
Beginning balance	4,969	4,671
Provision	6,848	4,349
Payments/credits	(7,236)	(5,719)
Ending balance	$ 4,581	$ 3,301