SCHEDULE I - CONDENSED FINANCIAL INFORMATION OF PARENT - BALANCE SHEETS (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
ASSETS
Cash and cash equivalents	$ 960	$ 108
Due from affiliates	20	32
Income taxes receivable	113	112
Other current assets	364	324
Total current assets	4,511	3,339
Due from affiliates	780	742
Deferred income taxes	136	155
Other long-term assets	753	732
Total assets	66,623	65,665	$ 60,638
Liabilities and shareholders’ equity:
Current portion of long-term debt	1,540	1,526
Due to affiliates	45	5
Other current liabilities	1,016	866
Total current liabilities	6,839	9,150
Long-term debt	21,781	20,785
Due to affiliates	234	195
Commitments and contingencies (Note 4)
Total shareholders’ equity	23,373	19,929
Total liabilities and shareholders’ equity	66,623	65,665
Parent Company [Member]
ASSETS
Cash and cash equivalents	366	6	$ 14	$ 104
Due from affiliates	58	98
Income taxes receivable	42	0
Other current assets	26	34
Total current assets	492	138
Investments in subsidiaries	33,898	32,604
Due from affiliates	1	3
Deferred income taxes	2,187	1,766
Other long-term assets	717	682
Total assets	37,295	35,193
Liabilities and shareholders’ equity:
Current portion of long-term debt	850	1,399
Due to affiliates	224	369
Income taxes payable, net	0	274
Other current liabilities	536	561
Total current liabilities	1,610	2,603
Long-term debt	7,317	8,856
Due to affiliates	4,375	3,138
Other long-term liabilities	620	667
Commitments and contingencies (Note 4)
Total shareholders’ equity	23,373	19,929
Total liabilities and shareholders’ equity	$ 37,295	$ 35,193