Long-term Debt and Other Borrowings - Gains and Losses Resulting from Changes in Fair Value of Interest Rate Swaps and Hedged Fixed Rate Debt (Details) - USD ($) $ in Millions	3 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Debt Disclosure [Abstract]
Gain (loss) on fair value of interest rate swaps	$ (40)	$ 52
Gain (loss) on fair value of hedged fixed-rate debt	40	(52)
Net gain (loss) recorded in interest on borrowings	$ 0	$ 0

Amount of gain (loss) from the increase (decrease) in fair value of derivative and nonderivative instruments designated as fair value hedging instruments recognized in the income statement.

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-Name Accounting Standards Codification
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-SubTopic 25
-Section 50
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Amount of the increase (decrease) in fair value of the hedged item in a fair value hedge recognized in the income statement.

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Total amount of gain (loss) derived from fair value hedges recognized in earnings in the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
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