Asbestos-Related Liabilities (Summary of Asbestos Claims Cash Payments by Company) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Liability for Asbestos and Environmental Claims [Abstract]
Asbestos-related payments	$ 30	$ 30	$ 30
Settled claims payments (included in asbestos-related payments above)	$ 24	$ 23	$ 22

Amount, after effects of reinsurance, of payments to settle insured claims and pay costs incurred in the claims settlement process attributable to asbestos and environmental claims.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=65670824&loc=d3e14764-158437

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