Insurance Claim Reserves Insurance Claim Reserves (Details) - Asbestos and Environmental - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Business Insurance [Member] \| Environmental Issue [Member]
Liability for claims and claim adjustment expense
Increase (decrease) to asbestos and environmental reserves	$ 55	$ 65	$ 55	$ 65

The increase (decrease) during the reporting period in asbestos and environmental claims reserve, net of reinsurance recoveries.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 3
-Subparagraph (b),(c)
-URI http://asc.fasb.org/extlink&oid=99382578&loc=d3e14764-158437

Name:	us-gaap_LiabilityForAsbestosAndEnvironmentalClaimsNetPeriodIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration