CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Adoption of ASU	Common Stock	Additional Paid-in Capital	Retained Earnings	Retained Earnings Adoption of ASU	Accumulated Other Comprehensive Loss	Treasury Stock	Non-controlling Interest	Non-controlling Interest Adoption of ASU
Balance, beginning of period at Sep. 30, 2017	$ 2,064,461		$ 2,806	$ 4,517,635	$ 2,395,218		$ (95,850)	$ (4,755,348)	$ 0
Increase (decrease) in stockholders' equity
Consolidation of variable interest entity	167,966								167,966
Net (loss) income	1,615,892				1,658,405				(42,513)
Other comprehensive income (loss)	8,281						16,597		(8,316)
Cash dividends	(333,041)				(333,041)
Exercises of stock options	138,456		27	138,429
Share-based compensation expense	62,316			62,316
Common stock purchases for employee stock purchase plan	(341)			(341)
Purchases of common stock	(663,220)							(663,220)
Employee tax withholdings related to restricted share vesting	(8,246)							(8,246)
Other	(2,563)		3	(2,566)
Balance, end of period at Sep. 30, 2018	3,049,961	$ (2,584)	2,836	4,715,473	3,720,582	$ (1,482)	(79,253)	(5,426,814)	117,137	$ (1,102)
Increase (decrease) in stockholders' equity
Net (loss) income	854,135				855,365				(1,230)
Other comprehensive income (loss)	(33,228)						(32,712)		(516)
Cash dividends	(338,974)				(338,974)
Exercises of stock options	76,234		15	76,219
Share-based compensation expense	58,874			58,874
Purchases of common stock	(664,803)							(664,803)
Employee tax withholdings related to restricted share vesting	(5,987)							(5,987)
Other	(422)		2	(424)
Balance, end of period at Sep. 30, 2019	$ 2,993,206	$ 35,138	2,853	4,850,142	4,235,491	$ 35,138	(111,965)	(6,097,604)	114,289
Increase (decrease) in stockholders' equity
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201409Member
Net (loss) income	$ (3,399,558)				(3,408,716)				9,158
Other comprehensive income (loss)	(8,946)						3,135		(12,081)
Cash dividends	(343,578)				(343,578)
Exercises of stock options	159,533		21	159,512
Share-based compensation expense	74,411			74,411
Purchases of common stock	(405,692)							(405,692)
Profarma retail equity offering	66,355			(1,567)					67,922
Employee tax withholdings related to restricted share vesting	(9,787)							(9,787)
Other	(718)		4	(722)
Balance, end of period at Sep. 30, 2020	$ (839,636)		$ 2,878	$ 5,081,776	$ 518,335		$ (108,830)	$ (6,513,083)	$ 179,288
Increase (decrease) in stockholders' equity
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201602Member