Schedule I - Condensed Financial Information - Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current Assets
Cash and temporary cash investments	$ 895	$ 797
Taxes receivable	49	76
Prepayments	187	178
Other current assets	122	177
TOTAL CURRENT ASSETS	3,864	3,537
Investments in subsidiaries	1,766	2,001
Goodwill	440	428
Other noncurrent assets	6,541	4,973
TOTAL ASSETS	53,920	48,111	$ 48,255
Current Liabilities
Long-term debt due within one year	650	1,298
Term Loan	825	0
Notes payable	1,741	577
Accounts payable	1,187	1,286
Accrued taxes	61	108
Other current liabilities	363	386
TOTAL CURRENT LIABILITIES	6,207	4,902
Long-term debt	17,495	14,731
Shareholders’ Equity
Equity	16,726	15,418
TOTAL LIABILITIES AND EQUITY	53,920	48,111
Parent Company
Current Assets
Cash and temporary cash investments	9	9	$ 13	$ 51
Taxes receivable	43	45
Term loan receivable from affiliated companies	825	0
Accounts receivable from affiliated companies	536	687
Prepayments	33	36
Other current assets	12	18
TOTAL CURRENT ASSETS	1,458	795
Investments in subsidiaries	16,707	15,110
Goodwill	406	406
Deferred income tax	69	18
Long-term debt receivable from affiliated companies	900	900
Other noncurrent assets	2	2
TOTAL ASSETS	19,542	17,231
Current Liabilities
Long-term debt due within one year	3	2
Term Loan	825	0
Notes payable	495	331
Accounts payable	9	0
Accounts payable to affiliated companies	274	274
Accrued taxes	2	0
Other current liabilities	13	10
TOTAL CURRENT LIABILITIES	1,621	617
Total Liabilities	1,621	617
Long-term debt	1,195	1,195
Shareholders’ Equity
Common stock, including additional paid-in capital	7,151	6,331
Retained earnings	9,575	9,088
Equity	16,726	15,419
TOTAL LIABILITIES AND EQUITY	$ 19,542	$ 17,231