Retirement Benefits - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Portion of pension and OPEB obligation attributed to disclosed plans (as a percent)			99.00%
Defined contribution plan, employer contribution	$ 28,000,000	$ 39,000,000	$ 117,000,000	$ 118,000,000
Pension Plan [Member] | NETHERLANDS [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement	16,000,000		16,000,000
Pension Plan [Member] | UNITED KINGDOM [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement	(12,000,000)	0	(32,000,000)	0
Defined benefit pension plans contributions			61,000,000
Defined benefit plan, estimated future employer additional contributions, remainder of fiscal year	23,000,000		23,000,000
Pension Plan [Member] | UNITED STATES [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement	0	(1,000,000)	0	(1,000,000)
Defined benefit pension plans contributions			50,000,000
Defined benefit plan, estimated future employer additional contributions, remainder of fiscal year	0		0
Pension Plan [Member] | Other Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement	14,000,000	0	14,000,000	0
Defined benefit pension plans contributions			11,000,000
Defined benefit plan, estimated future employer additional contributions, remainder of fiscal year	3,000,000		3,000,000
Pension Costs [Member] | Pension Plan [Member] | UNITED KINGDOM [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement	(12,000,000)		(32,000,000)
Accounting Standards Update 2017-07 [Member]
Defined Benefit Plan Disclosure [Line Items]
Reclassification For Presentation	$ 77,000,000	$ 67,000,000	$ 217,000,000	$ 192,000,000