Benefit Obligations (Schedule of Contributions to Multiemployer Defined Benefit Pension Plans) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Retirement Benefits [Abstract]
Multiemployer plans, funded status	At least 80 percent	At least 80 percent	At least 80 percent
Multiemployer defined benefit plan	$ 8	$ 8	$ 7

Indicate whether the multiemployer plan is less than 65 percent funded, between 65 and less than 80 percent funded, or at least 80 percent funded. The acceptable values are: (1) "less than 65 percent", (2) "between 65 and less than 80 percent", (3) "at least 80 percent", and (4) "NA". A multiemployer plan is a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 5
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450657-114947

Name:	us-gaap_MultiemployerPlansFundedStatus
Namespace Prefix:	us-gaap_
Data Type:	us-types:fundedStatusItemType
Balance Type:	na
Period Type:	duration