Summary of Significant Accounting Policies (Supplemental Disclosure of Cash Flow Information) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Summary of Significant Accounting Policies [Abstract]
Accruals for capital expenditures		$ 592	$ 412	$ 584
Interest	[1]	248	205	178
Income taxes, net of refunds received		474	567	405
Interest costs capitalized		$ 54	$ 49	$ 36

[1] Included in this amount are approximately $54 million, $49 million and $36 million of interest costs that were capitalized as part of property, plant and equipment, net of accumulated depreciation, in 2019, 2018 and 2017, respectively.