CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) - USD ($) shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
OPERATING REVENUE	$ 4,887	$ 5,167	$ 14,840	$ 15,587
OPERATING EXPENSES
Cost of services and products (exclusive of depreciation and amortization)	2,151	2,236	6,402	6,703
Selling, general and administrative	654	850	2,172	2,598
Depreciation and amortization	951	1,193	3,142	3,515
Total operating expenses	3,756	4,279	11,716	12,816
OPERATING INCOME	1,131	888	3,124	2,771
OTHER (EXPENSE) INCOME
Interest expense	(377)	(409)	(1,150)	(1,272)
Other (expense) income, net	(38)	1	48	(73)
Total other expense, net	(415)	(408)	(1,102)	(1,345)
INCOME BEFORE INCOME TAXES	716	480	2,022	1,426
Income tax expense	172	114	497	369
NET INCOME	$ 544	$ 366	$ 1,525	$ 1,057
BASIC AND DILUTED EARNINGS PER COMMON SHARE
BASIC (in dollars per share)	$ 0.51	$ 0.34	$ 1.42	$ 0.98
DILUTED (in dollars per share)	$ 0.51	$ 0.34	$ 1.41	$ 0.98
WEIGHTED-AVERAGE COMMON SHARES OUTSTANDING
BASIC (in shares)	1,062,084	1,080,505	1,077,106	1,078,672
DILUTED (in shares)	1,069,157	1,085,666	1,083,879	1,083,368