CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
OPERATING REVENUE	$ 5,192	$ 5,375	$ 10,420	$ 10,802
OPERATING EXPENSES
Cost of services and products (exclusive of depreciation and amortization)	2,232	2,243	4,467	4,543
Selling, general and administrative	895	960	1,748	1,892
Depreciation and amortization	1,162	1,196	2,322	2,384
Goodwill impairment	0	0	0	6,506
Total operating expenses	4,289	4,399	8,537	15,325
OPERATING INCOME (LOSS)	903	976	1,883	(4,523)
OTHER (EXPENSE) INCOME
Interest expense	(414)	(518)	(863)	(1,041)
Other income (loss), net	24	44	(74)	39
Total other expense, net	(390)	(474)	(937)	(1,002)
INCOME (LOSS) BEFORE INCOME TAXES	513	502	946	(5,525)
Income tax expense	136	131	255	269
NET INCOME (LOSS)	$ 377	$ 371	$ 691	$ (5,794)
BASIC AND DILUTED EARNINGS (LOSS) PER COMMON SHARE
BASIC (in dollars per share)	$ 0.35	$ 0.35	$ 0.64	$ (5.41)
DILUTED (in dollars per share)	$ 0.35	$ 0.35	$ 0.64	$ (5.41)
WEIGHTED-AVERAGE COMMON SHARES OUTSTANDING
BASIC (in shares)	1,079,475	1,071,341	1,077,755	1,070,110
DILUTED (in shares)	1,082,567	1,072,813	1,082,218	1,070,110