Fair Value of Financial Instruments (Details) - Fair Value, Measurements, Recurring - Significant Other Observable Inputs (Level 2) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities-Long-term debt, excluding finance leases	$ 10,134	$ 10,196
Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities-Long-term debt, excluding finance leases	$ 10,225	$ 10,244

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13433-108611

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