Acquisitions, Investments and Dispositions - Pro Forma Supplemental Information (Details) - USD ($) $ in Millions		12 Months Ended
	Dec. 13, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2017
Business Combinations [Abstract]
Revenues		$ 12,246	$ 12,574	$ 12,337	$ 12,033
Net income		$ 1,101	$ 1,343	1,382	1,525
If Acquired January 1, 2017 (a)(b)
Revenue				12,655	12,331
Net income				1,279	1,612
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Interest expense				37	38
Business acquisition, pre-tax gain from interests in projects	$ 131				131
Pro Forma
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Income from equity method investment				33	$ 32
Term Loan
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Short-term borrowings				$ 825
Fixed interest rate						4.64%