Benefit Plans (Narrative) (Details) - USD ($)	1 Months Ended	3 Months Ended				12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 270,000,000
Lump sum payment	277,000,000
One-time settlement charge relating to lump sum distributions		$ 81,000,000	$ 0	$ 0	$ 0		$ 81,000,000
Amounts charged to expense for defined contribution plans						$ 85,000,000	83,000,000	$ 93,000,000
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions						41,000,000	24,000,000
Net periodic benefit cost						17,000,000	49,000,000	14,000,000
Accumulated benefit obligation	8,200,000,000	8,200,000,000				7,400,000,000	8,200,000,000
Projected benefit obligation	413,000,000	413,000,000				7,598,000,000	413,000,000
Accumulated benefit obligation	364,000,000	364,000,000				7,239,000,000	364,000,000
Fair value of plan assets	124,000,000	124,000,000				7,012,000,000	124,000,000
Defined benefit plan, plan assets, amount	8,015,000,000	8,015,000,000				7,138,000,000	8,015,000,000	7,475,000,000
Pension [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected future employer contributions						$ 50,000,000
Pension [Member] | Emerging Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Composition of plan assets						1.00%
Pension [Member] | Below grade investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Composition of plan assets						7.00%
Pension [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation percentage						55.00%
Pension [Member] | Equity Securities [Member] | Emerging Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Composition of plan assets						1.00%
Pension [Member] | Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation percentage						45.00%
Pension [Member] | Fixed Income Securities [Member] | Below grade investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Composition of plan assets						14.00%
Postretirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions						$ 0	270,000,000
Net periodic benefit cost						48,000,000	79,000,000	78,000,000
Defined benefit plan, plan assets, amount	270,000,000	270,000,000				211,000,000	270,000,000	0
Expected future employer contributions						60,000,000
Postretirement Benefit Plan [Member] | Emerging Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount						$ 0
Postretirement Benefit Plan [Member] | Below grade investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Composition of plan assets						6.00%
Postretirement Benefit Plan [Member] | Fixed Income Securities [Member] | Below grade investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Composition of plan assets						13.00%
Postretirement Benefit Plan [Member] | Defined Benefit Plan, Common Collective Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	148,000,000	148,000,000					148,000,000
Postretirement Benefit Plan [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	122,000,000	122,000,000					122,000,000
Fair Value, Inputs, Level 1, 2 and 3 [Member] | Postretirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	0	0					0
Level 3 [Member] | Postretirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets, amount	$ 0	$ 0				$ 0	0
Accounting Standards Update 2017-07 [Member] | Cost of Sales [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost							12,000,000	(19,000,000)
Accounting Standards Update 2017-07 [Member] | Marketing, Adminstration and Research Costs [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost							24,000,000	(12,000,000)
Accounting Standards Update 2017-07 [Member] | Asset Impairment and Exit Costs [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost							$ 1,000,000	$ (30,000,000)