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, 2017	Sep. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	$ 5,528	$ 5,019
Investments measured at net asset value	$ 2,259	$ 1,877
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	$ 1,918	$ 1,855
Fair Value, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	900	882
Fair Value, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	451	405
U.S. equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	1,759	1,678
Investments measured at net asset value	$ 357	$ 301
Percentage of defined benefit plan assets	32.00%	33.00%
U.S. equities [Member] | Fair Value, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	$ 1,059	$ 1,081
U.S. equities [Member] | Fair Value, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	5	4
U.S. equities [Member] | Fair Value, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	338	292
International equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	1,469	1,234
Investments measured at net asset value	$ 739	$ 599
Percentage of defined benefit plan assets	27.00%	25.00%
International equities [Member] | Fair Value, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	$ 724	$ 627
International equities [Member] | Fair Value, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	6	8
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	276	257
Investments measured at net asset value	$ 276	$ 257
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	797	648
Investments measured at net asset value	$ 283	$ 172
Percentage of defined benefit plan assets	14.00%	13.00%
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	514	476
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	771	752
Investments measured at net asset value	$ 399	$ 357
Percentage of defined benefit plan assets	14.00%	15.00%
Government bonds [Member] | Fair Value, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	$ 3	$ 3
Government bonds [Member] | Fair Value, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	369	392
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	132	122
Investments measured at net asset value	$ 132	$ 122
Percentage of defined benefit plan assets	2.00%	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	324	328
Investments measured at net asset value	$ 73	$ 69
Percentage of defined benefit plan assets	6.00%	7.00%
Other [Member] | Fair Value, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	$ 132	$ 144
Other [Member] | Fair Value, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	6	2
Other [Member] | Fair Value, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair values of defined benefit plan assets	$ 113	$ 113