Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Sep. 30, 2020
Current assets:
Cash and cash equivalents	$ 278,314	$ 244,597	$ 126,259	$ 86,865	$ 120,817	$ 159,621	$ 25,812	$ 66,056
Trade receivables, net of allowances	57,660	74,718	152,745	68,290	90,159	101,513	171,685	63,057
Inventories	195,600	198,388	230,219	296,576	281,790	299,432	281,026	277,724
Prepaid expenses	13,595	13,668	16,747	22,526	17,212	20,522	18,203	17,641
Other current assets	16,123	24,630	29,217	23,090	9,152	6,861	9,313	2,827
Total current assets	561,292	556,001	555,187	497,347	519,130	587,949	506,039	427,305
Property, plant and equipment, net	501,023	494,895	507,198	513,930	517,913	495,961	474,340	435,304
Goodwill	994,271	994,155	994,155	993,995	993,995	987,440	987,440	992,513	$ 951,390
Intangible assets, net	199,497	210,800	222,378	233,998	245,835	247,606	260,128	272,692
Other assets	87,793	89,369	91,649	94,068	94,754	83,041	76,721	77,578
Total assets	2,343,876	2,345,220	2,370,567	2,333,338	2,371,627	2,401,997	2,304,668	2,205,392	2,180,727
Current liabilities:
Accounts payable	56,015	53,010	51,921	48,563	48,987	83,034	76,228	64,490
Accrued rebates	60,974	49,371	65,074	54,556	50,479	44,491	31,723	49,150	44,300
Accrued interest	260	130	58	140	4,436	4,367	46	214
Current portion of long-term debt obligations	6,000	6,000	6,000	6,000	6,000	4,500
Accrued expenses and other liabilities	66,467	58,581	69,452	67,488	72,589	68,660	66,986	49,984
Total current liabilities	189,716	167,092	192,505	176,747	182,491	205,052	174,983	163,838
Deferred income taxes	59,509	69,328	66,695	68,324	67,467	66,454	60,067	49,315
Long-term debt — less current portion	580,265	581,418	582,572	583,726	584,879	586,033	505,284	464,999
Other non-current liabilities	104,073	105,485	109,405	109,404	106,083	93,601	86,074	85,665
Total liabilities	933,563	923,323	951,177	938,201	940,920	951,140	826,408	763,817
Commitments and contingencies (Note 17)
Stockholders’ equity:
Preferred stock, $0.001 par value; 1,000,000 shares authorized and no shares issued and outstanding at September 30, 2023 and September 30, 2022, respectively
Additional paid-in capital	1,662,322	1,653,714	1,641,321	1,633,827	1,630,378	1,626,115	1,628,581	1,622,516
Accumulated deficit	(64,377)	(103,608)	(138,248)	(156,473)	(126,738)	(125,340)	(150,476)	(181,096)
Accumulated other comprehensive income (loss)	1,878	691	(3,262)	(1,796)
Treasury stock, at cost, 8,268,423 shares at September 30, 2023 and 4,116,570 shares at September 30, 2022	(189,666)	(129,056)	(80,576)	(80,576)	(73,088)	(50,073)
Total stockholders’ equity	1,410,313	1,421,897	1,419,390	1,395,137	1,430,707	1,450,857	1,478,260	1,441,575	$ 1,421,495	$ 1,302,504
Total liabilities and stockholders’ equity	2,343,876	2,345,220	2,370,567	2,333,338	2,371,627	2,401,997	2,304,668	2,205,392
Common Class A [Member]
Stockholders’ equity:
Common stock	$ 156	$ 156	$ 155	$ 155	$ 155	$ 155	$ 155	$ 155