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Debt - Schedule of Debt Instruments (Details)	Dec. 31, 2018 GBP (£)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)
Debt Instrument [Line Items]
Long-term debt		$ 176,306,000	$ 177,453,000
Capital lease obligations		69,000	745,000
Total debt		4,321,676,000	4,310,189,000
Less AmerisourceBergen Corporation current portion		24,927,000	13,976,000
Total, net of current portion		4,165,400,000	4,158,532,000
Revolving credit note
Debt Instrument [Line Items]
Maximum borrowing capacity		75,000,000
Long-term debt		0	0
Term loans due in 2020
Debt Instrument [Line Items]
Long-term debt		399,601,000	398,665,000
Overdraft facility due 2021 (£30,000)
Debt Instrument [Line Items]
Maximum borrowing capacity \| £	£ 30,000,000
Long-term debt		24,891,000	13,269,000
Receivables securitization facility due 2021
Debt Instrument [Line Items]
Maximum borrowing capacity		1,450,000,000
Long-term debt		500,000,000	500,000,000
Multi-currency revolving credit facility due 2023
Debt Instrument [Line Items]
Maximum borrowing capacity		1,400,000,000.0
Long-term debt		0	0
$500,000, 3.50% senior notes due 2021
Debt Instrument [Line Items]
Principal amount		$ 500,000,000
Interest rate	3.50%	3.50%
Long-term debt		$ 498,521,000	498,392,000
$500,000, 3.40% senior notes due 2024
Debt Instrument [Line Items]
Principal amount		$ 500,000,000
Interest rate	3.40%	3.40%
Long-term debt		$ 497,377,000	497,255,000
$500,000, 3.25% senior notes due 2025
Debt Instrument [Line Items]
Principal amount		$ 500,000,000
Interest rate	3.25%	3.25%
Long-term debt		$ 495,802,000	495,632,000
$750,000, 3.45% senior notes due 2027
Debt Instrument [Line Items]
Principal amount		$ 750,000,000
Interest rate	3.45%	3.45%
Long-term debt		$ 742,468,000	742,258,000
$500,000, 4.25% senior notes due 2045
Debt Instrument [Line Items]
Principal amount		$ 500,000,000
Interest rate	4.25%	4.25%
Long-term debt		$ 494,352,000	494,298,000
$500,000, 4.30% senior notes due 2047
Debt Instrument [Line Items]
Principal amount		$ 500,000,000
Interest rate	4.30%	4.30%
Long-term debt		$ 492,289,000	492,222,000
Nonrecourse debt
Debt Instrument [Line Items]
Less AmerisourceBergen Corporation current portion		$ 131,349,000	$ 137,681,000