CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) - USD ($) shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Abstract]
OPERATING REVENUE	$ 4,924	$ 5,192	$ 9,953	$ 10,420
OPERATING EXPENSES
Cost of services and products (exclusive of depreciation and amortization)	2,115	2,232	4,251	4,467
Selling, general and administrative	762	895	1,518	1,748
Depreciation and amortization	1,041	1,162	2,191	2,322
Total operating expenses	3,918	4,289	7,960	8,537
OPERATING INCOME	1,006	903	1,993	1,883
OTHER (EXPENSE) INCOME
Interest expense	(384)	(414)	(773)	(863)
Other income (expense), net	52	24	86	(74)
Total other expense, net	(332)	(390)	(687)	(937)
INCOME BEFORE INCOME TAXES	674	513	1,306	946
Income tax expense	168	136	325	255
NET INCOME	$ 506	$ 377	$ 981	$ 691
BASIC AND DILUTED EARNINGS PER COMMON SHARE
BASIC (in dollars per share)	$ 0.47	$ 0.35	$ 0.90	$ 0.64
DILUTED (in dollars per share)	$ 0.46	$ 0.35	$ 0.90	$ 0.64
WEIGHTED-AVERAGE COMMON SHARES OUTSTANDING
BASIC (in shares)	1,086,453	1,079,475	1,084,464	1,077,755
DILUTED (in shares)	1,093,402	1,082,567	1,092,494	1,082,218