CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) - USD ($) shares in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Statement [Abstract]
OPERATING REVENUE	$ 5,029	$ 5,228
OPERATING EXPENSES
Cost of services and products (exclusive of depreciation and amortization)	2,136	2,235
Selling, general and administrative	756	853
Depreciation and amortization	1,150	1,160
Total operating expenses	4,042	4,248
OPERATING INCOME	987	980
OTHER (EXPENSE) INCOME
Interest expense	(389)	(449)
Other income (expense), net	34	(98)
Total other expense, net	(355)	(547)
INCOME BEFORE INCOME TAXES	632	433
Income tax expense	157	119
NET INCOME	$ 475	$ 314
BASIC AND DILUTED EARNINGS PER COMMON SHARE
BASIC (in dollars per share)	$ 0.44	$ 0.29
DILUTED (in dollars per share)	$ 0.44	$ 0.29
WEIGHTED-AVERAGE COMMON SHARES OUTSTANDING
BASIC (in shares)	1,082,474	1,075,459
DILUTED (in shares)	1,091,586	1,081,754