Leases (Narrative) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Leases [Line Items]
Assets recorded under finance leases	$ 222	$ 220
Finance Lease, Accumulated Depreciation	134	$ 127
Current Portion Of Long-Term Debt [Member]
Leases [Line Items]
Finance Leases	35
Long-term Debt [Member]
Leases [Line Items]
Finance Leases	$ 58

Present value of lessee's discounted obligation for lease payments from finance lease.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918701-209980

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918627-209977

Name:	us-gaap_FinanceLeaseLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant