Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Short-term Debt (Details) - USD ($)	Jul. 19, 2018	Jun. 30, 2018	Sep. 30, 2017
Short-term Debt [Line Items]
Commercial paper borrowings outstanding		$ 0	$ 350,000,000
Weighted average interest rate of commercial paper outstanding			1.26%
Current portion of long-term debt		$ 0	$ 250,000,000
Stated interest rate percentage			5.65%
Subsequent Event [Member]
Short-term Debt [Line Items]
Weighted average interest rate of commercial paper outstanding	2.19%
Securities Purchase Agreement [Member] \| Commercial paper [Member] \| Subsequent Event [Member]
Short-term Debt [Line Items]
Debt Instrument, Face Amount	$ 675,000,000