Retirement Plans (Schedule Of Fair Values Of Defined Benefit Plan Assets Organized By Asset Class And Fair Value Hierarchy Of ASC 820) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	$ 5,476	$ 5,528
Investments measured at net asset value	$ 2,257	$ 2,259
Percentage of defined benefit plan assets	100.00%	100.00%
Fair Value, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	$ 1,670	$ 1,918
Fair Value, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	1,078	900
Fair Value, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	471	451
U.S. equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	1,643	1,759
Investments measured at net asset value	$ 320	$ 357
Percentage of defined benefit plan assets	30.00%	32.00%
U.S. equities [Member] | Fair Value, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	$ 968	$ 1,059
U.S. equities [Member] | Fair Value, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	5	5
U.S. equities [Member] | Fair Value, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	350	338
International equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	1,361	1,469
Investments measured at net asset value	$ 745	$ 739
Percentage of defined benefit plan assets	25.00%	27.00%
International equities [Member] | Fair Value, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	$ 595	$ 724
International equities [Member] | Fair Value, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	21	6
International equities [Member] | Fair Value, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	0	0
Emerging market equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	243	276
Investments measured at net asset value	$ 243	$ 276
Percentage of defined benefit plan assets	5.00%	5.00%
Emerging market equities [Member] | Fair Value, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	$ 0	$ 0
Emerging market equities [Member] | Fair Value, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	0	0
Emerging market equities [Member] | Fair Value, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	0	0
Corporate bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	1,119	797
Investments measured at net asset value	$ 423	$ 283
Percentage of defined benefit plan assets	20.00%	14.00%
Corporate bonds [Member] | Fair Value, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	$ 0	$ 0
Corporate bonds [Member] | Fair Value, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	696	514
Corporate bonds [Member] | Fair Value, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	0	0
Government bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	788	771
Investments measured at net asset value	$ 438	$ 399
Percentage of defined benefit plan assets	14.00%	14.00%
Government bonds [Member] | Fair Value, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	$ 0	$ 3
Government bonds [Member] | Fair Value, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	350	369
Government bonds [Member] | Fair Value, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	0	0
High yield bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	10	132
Investments measured at net asset value	$ 10	$ 132
Percentage of defined benefit plan assets	0.00%	2.00%
High yield bonds [Member] | Fair Value, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	$ 0	$ 0
High yield bonds [Member] | Fair Value, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	0	0
High yield bonds [Member] | Fair Value, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	0	0
Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	312	324
Investments measured at net asset value	$ 78	$ 73
Percentage of defined benefit plan assets	6.00%	6.00%
Other [Member] | Fair Value, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	$ 107	$ 132
Other [Member] | Fair Value, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	6	6
Other [Member] | Fair Value, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	$ 121	$ 113