Variable Interest Entity - Financial Position of Variable Interest Entity (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018
Variable Interest Entity [Line Items]
Cash and cash equivalents	$ 3,691,938	$ 3,374,194	$ 2,875,750	$ 2,492,516
Inventories	11,102,566	11,060,254
Property and equipment, net	1,421,768	1,770,516
Goodwill	6,704,133	6,705,507
Other long-term assets	800,263	269,067
TOTAL ASSETS	42,042,262	39,171,980
Long-term debt	4,145,194	4,172,892
Deferred income taxes	1,843,910	1,860,195
Other long-term liabilities	479,659	98,812
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Cash and cash equivalents	15,589	9,431
Accounts receivables, net	129,875	154,491
Inventories	164,998	185,602
Prepaid expenses and other	57,821	64,119
Property and equipment, net	24,700	30,961
Goodwill	82,309	82,309
Other intangible assets	75,655	74,429
Other long-term assets	53,381	9,169
TOTAL ASSETS	604,328	610,511
Accounts payable	168,452	165,053
Accrued expenses and other	34,141	49,191
Short-term debt	90,496	106,439
Long-term debt	47,768	60,973
Deferred income taxes	36,858	42,371
Other long-term liabilities	40,886	5,303
Total liabilities	$ 418,601	$ 429,330