Condensed Consolidated Balance Sheets (unaudited) (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2019	Sep. 30, 2018	Jun. 30, 2018
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 15,967	$ 9,760	$ 16,261
Accumulated depreciation and amortization	$ 1,115,273	$ 1,074,521	$ 1,069,070
Common stock, par value (in usd per share)	$ 2.25	$ 2.25	$ 2.25
Common stock, shares authorized (in shares)	40,000,000	40,000,000	40,000,000
Common stock, shares issued (in shares)	26,781,785	26,781,785	26,781,785
Common stock, shares outstanding (in shares)	26,781,785	26,781,785	26,781,785