Annual report pursuant to Section 13 and 15(d)

Debt - Schedule of Carrying Values and Estimated Fair Values of Debt Instruments (Details)

v3.20.4
Debt - Schedule of Carrying Values and Estimated Fair Values of Debt Instruments (Details) - USD ($)
$ in Millions
Dec. 31, 2020
Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Carrying Amount, Debt $ 17,580 $ 17,579
Senior Notes [Member] | Carrying Amount [Member] | Fair Value, Inputs, Level 2 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Carrying Amount, Debt [1] 16,950 16,950
Senior Notes [Member] | Carrying Amount [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Carrying Amount, Debt [2] 800 800
Senior Notes [Member] | Estimated Fair Value [Member] | Fair Value, Inputs, Level 2 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Senior Notes, Estimated Fair Value [1] 19,113 18,320
Senior Notes [Member] | Estimated Fair Value [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Senior Notes, Estimated Fair Value [2] 1,036 934
Credit facilities [Member] | Carrying Amount [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Carrying Amount, Debt [3] 0 0
Credit facilities [Member] | Estimated Fair Value [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Lines of Credit, Fair Value Disclosure [3] $ 0 $ 0
[1] The Level 2 estimated fair value was based on quotes obtained from broker-dealers or market makers of these senior notes and other similar instruments.
[2] The Level 3 estimated fair value was calculated based on inputs that are observable in the market or that could be derived from, or corroborated with, observable market data, including interest rates based on debt issued by parties with comparable credit ratings to us and inputs that are not observable in the market.
[3] The Level 3 estimated fair value approximates the principal amount because the interest rates are variable and reflective of market rates and the debt may be repaid, in full or in part, at any time without penalty