Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended									12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Revenue	$ 49,244,768	$ 45,366,777	$ 47,417,639	$ 47,864,742	$ 45,637,802	$ 45,239,265	$ 43,319,602	$ 45,392,452		$ 189,893,926	$ 179,589,121	$ 167,939,635
Gross profit	1,346,847	1,225,716	1,388,107	1,231,214	1,184,737	1,231,239	1,424,756	1,297,580		5,191,884	5,138,312	4,612,317
Distribution, selling, and administrative expenses; depreciation; and amortization	818,303	762,300	787,208	790,468	830,489	764,539	751,802	779,085		3,158,279	3,125,915
Employee severance, litigation, and other	6,641,681	58,585	67,732	39,309	174,407	60,006	55,389	40,672		6,807,307	330,474
Impairment of PharMEDium assets	0	0	223,652	138,000	0	0	570,000	0		361,652	570,000	0
Operating (loss) income	(6,113,137)	404,831	309,515	263,437	179,841	406,694	47,565	477,823		(5,135,354)	1,111,923	1,443,685
Net (loss) income	(4,844,505)	287,268	971,111	186,568	132,307	302,002	28,073	391,753		(3,399,558)	854,135	1,615,892
Net income attributable to AmerisourceBergen Corporation	$ (4,846,072)	$ 289,439	$ 960,277	$ 187,640	$ 132,619	$ 301,959	$ 27,135	$ 393,652		$ (3,408,716)	$ 855,365	$ 1,658,405
Earnings per share operations:
Basic (usd per share)	$ (23.74)	$ 1.42	$ 4.68	$ 0.91	$ 0.64	$ 1.44	$ 0.13	$ 1.86		$ (16.65)	$ 4.07	$ 7.61
Diluted (usd per share)	$ (23.74)	$ 1.41	$ 4.64	$ 0.90	$ 0.63	$ 1.43	$ 0.13	$ 1.84		$ (16.65)	$ 4.04	$ 7.53
Gain (loss) related to litigation settlement	$ 500		$ 100	$ 8,500	$ 3,100	$ 3,500	$ 52,000	$ 87,300		$ 9,100	$ 145,900	$ 35,900
LIFO charges (credit)	(35,800)	$ 6,100	23,900	13,300	57,200	(9,900)	(66,800)	(3,000)		7,422	(22,544)	67,324
PharMEDium remediation costs				$ 7,100	$ 6,700	$ 11,700	12,300	17,900
PharMEDium shutdown costs		400	5,000
Legal accrual										6,722,346	185,145	61,527
Income tax benefit								37,000		1,894,273	(112,971)	438,469
Loss on early retirement of debt		$ (22,200)								22,175	0	23,766
Tax benefit related to Switzerland tax reform										365,949	$ 2,196	$ 1,388
Estimated liability under the New York Opioid Stewardship Act	(14,800)							$ (22,000)	$ 22,000
Gain on sale of equity investment							$ 13,700
Opioid Lawsuits and Investigations
Earnings per share operations:
Legal accrual	6,600,000
Income tax benefit	1,100,000
PharMEDium Healthcare Holdings, Inc
Earnings per share operations:
Income tax benefit			$ (741,000)							$ 655,000
Adjustment to discrete tax benefits	(20,400)
Swiss Federal Tax Administration
Earnings per share operations:
Tax benefit related to Switzerland tax reform	$ 360,700