Income Taxes - Significant Components of Deferred Tax Liabilities (Assets) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019
Components of Deferred Tax Assets and Liabilities [Abstract]
Inventories	$ 1,309,815	$ 1,293,075
Property and equipment	94,521	143,851
Goodwill and other intangible assets	613,123	709,015
Right-of-use assets (Note 12)	113,220	0
Other	1,888	1,892
Gross deferred tax liabilities	2,132,567	2,147,833
Net operating loss and tax credit carryforwards	(263,171)	(318,868)
Allowance for doubtful accounts	(20,051)	(22,544)
Accrued expenses	(21,284)	(33,312)
Accrued litigation liability	(1,078,555)	0
Employee and retiree benefits	(13,891)	(12,420)
Goodwill and other intangible assets	(582,406)	0
Lease liabilities (Note 12)	(121,182)	0
Share-based compensation	(38,914)	(39,961)
Other	(79,916)	(60,215)
Gross deferred tax assets	(2,219,370)	(487,320)
Valuation allowance for deferred tax assets	411,648	199,682
Deferred tax assets, net of valuation allowance	(1,807,722)	(287,638)
Net deferred tax liabilities	$ 324,845	$ 1,860,195