SCHEDULE I - CONDENSED FINANCIAL INFORMATION OF PARENT - BALANCE SHEETS (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
ASSETS
Cash and cash equivalents	$ 190	$ 288
Due from affiliates	39	37
Income taxes receivable	68	110
Other current assets	257	202
Total current assets	3,645	3,341
Due from affiliates	688	598
Deferred income taxes	151	170
Other assets	974	792
Total assets	60,638	50,454	$ 47,786
Liabilities and shareholders’ equity:
Current portion of long-term debt	1,673	1,427
Due to affiliates	10	7
Other current liabilities	970	816
Total current liabilities	7,523	6,635
Long-term debt	21,611	16,445
Due to affiliates	37	35
Commitments and contingencies (Note 4)
Total shareholders’ equity	17,138	12,670
Total liabilities and equity	60,638	50,454
Parent Company [Member]
ASSETS
Cash and cash equivalents	14	104	$ 12	$ 4
Due from affiliates	93	83
Income taxes receivable	397	272
Other current assets	9	6
Total current assets	513	465
Investments in subsidiaries	28,778	17,924
Due from affiliates	3	2
Deferred income taxes	1,554	1,802
Other assets	572	656
Total assets	31,420	20,849
Liabilities and shareholders’ equity:
Current portion of long-term debt	1,498	500
Due to affiliates	287	280
Other current liabilities	527	396
Total current liabilities	2,312	1,176
Long-term debt	9,647	6,198
Due to affiliates	1,812	300
Other long-term liabilities	511	505
Commitments and contingencies (Note 4)
Total shareholders’ equity	17,138	12,670
Total liabilities and equity	$ 31,420	$ 20,849