Amount of payment for pension benefits. Excludes other postretirement benefits.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3536-108585

Name:	us-gaap_PensionContributions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Retirement Benefits - Narrative (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Oct. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure
Contributions to pension plans		$ 58	$ 58
Qualified Plan \| Pension Benefits
Defined Benefit Plan Disclosure
Contributions to pension plans	$ 55
Non-Qualified Plan \| Pension Benefits
Defined Benefit Plan Disclosure
Contributions to pension plans		$ 3