Retirement Plans (Schedule Of Net Funded Status) (Details) - USD ($) $ in Millions	3 Months Ended			12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Settlements			$ (1,200)
Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Funded status, December 31	$ (1,896)			$ (1,896)	$ (3,371)
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, January 1				13,683	14,438
Service cost				160	158	$ 161
Interest cost				536	580	597
Settlements				(1,295)	(1,222)
Actuarial (gain) loss				913	495
Defined Benefit Plan, Benefit Obligation, Business Combination				0	1
Defined Benefit Plan, Benefit Obligation, Divestiture				33	0
Plan amendments				3	0
Benefits Paid				(769)	(767)
Effect of foreign currency exchange rate movements				0	0
Benefit obligation, December 31	13,264			13,264	13,683	14,438
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, January 1				10,312	10,923
Actual return on plan assets				1,830	607
Company contributions				1,290	771
Benefits paid				(769)	(767)
Settlements	(9)	$ (8)		$ (1,295)	$ (1,222)
Defined benefit plan, plan assets, acquired plan assets				0	0
Effect of foreign currency exchange rate movements				$ 0	$ 0
Fair value of plan assets, December 31	11,368			11,368	10,312	10,923
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Funded status, December 31	(71)			(71)	(66)
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, January 1				219	204
Service cost				4	4	6
Interest cost				9	9	10
Settlements				(4)	(2)
Actuarial (gain) loss				2	35
Defined Benefit Plan, Benefit Obligation, Business Combination				5	0
Defined Benefit Plan, Benefit Obligation, Divestiture				0	0
Plan amendments				0	(1)
Benefits Paid				(8)	(9)
Effect of foreign currency exchange rate movements				20	(21)
Benefit obligation, December 31	247			247	219	204
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, January 1				153	155
Actual return on plan assets				10	17
Company contributions				10	8
Benefits paid				(8)	(9)
Settlements				$ (4)	$ (2)
Defined benefit plan, plan assets, acquired plan assets				3	0
Effect of foreign currency exchange rate movements				$ 12	$ (16)
Fair value of plan assets, December 31	$ 176			$ 176	$ 153	$ 155