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Basis of presentation and significant accounting policies and practices - Additional Information (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Antidilutive securities excluded from computation of earnings per share, Amount (in shares)	9	9
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, carrying value	$ 6,550		$ 5,803
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, estimated fair value	$ 7,060