Summary of Significant Accounting Policies - Goodwill and Other Intangible Assets (Details) - USD ($)		3 Months Ended								12 Months Ended
	Jul. 01, 2018	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, 2020	Sep. 30, 2019	Sep. 30, 2018	Oct. 01, 2019
Assets Held and Used [Line Items]
Goodwill impairment	$ 59,700,000
Goodwill impairment										$ 0	$ 0	$ 59,684,000
Indefinite-lived intangible asset impairment										0	0	0
Impairment of PharMEDium assets		$ 0	$ 0	$ 223,652,000	$ 138,000,000	$ 0	$ 0	$ 570,000,000	$ 0	361,652,000	$ 570,000,000	$ 0
Finite-lived intangible asset impairment					123,200,000			522,100,000
Property and equipment impairment					11,600,000			47,900,000
Operating lease, right-of-use asset		$ 443,522,000			3,200,000					$ 443,522,000			$ 526,281,000
PharMEDium Healthcare Holdings, Inc
Assets Held and Used [Line Items]
Carrying value of asset group, excluding goodwill								792,000,000
Fair value of asset group					$ 145,000,000			$ 222,000,000
Discount rate (as a percentage)					17.00%			15.00%
Customer relationships
Assets Held and Used [Line Items]
Finite-lived intangible asset impairment								$ 420,800,000
Trade names
Assets Held and Used [Line Items]
Finite-lived intangible asset impairment								79,900,000
Software technology
Assets Held and Used [Line Items]
Finite-lived intangible asset impairment								$ 21,400,000