CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
OPERATING REVENUE	$ 20,712	$ 21,458	$ 22,580
OPERATING EXPENSES
Cost of services and products (exclusive of depreciation and amortization)	8,934	9,134	9,999
Selling, general and administrative	3,464	3,715	4,165
Depreciation and amortization	4,710	4,829	5,120
Goodwill impairment	2,642	6,506	2,726
Total operating expenses	19,750	24,184	22,010
OPERATING INCOME (LOSS)	962	(2,726)	570
OTHER (EXPENSE) INCOME
Interest expense	(1,668)	(2,021)	(2,177)
Other (expense) income, net	(76)	(19)	44
Total other expense, net	(1,744)	(2,040)	(2,133)
LOSS BEFORE INCOME TAX EXPENSE	(782)	(4,766)	(1,563)
Income tax expense	450	503	170
NET LOSS	$ (1,232)	$ (5,269)	$ (1,733)
BASIC AND DILUTED LOSS PER COMMON SHARE
BASIC (in dollars per share)	$ (1.14)	$ (4.92)	$ (1.63)
DILUTED (in dollars per share)	$ (1.14)	$ (4.92)	$ (1.63)
WEIGHTED AVERAGE COMMON SHARES OUTSTANDING
BASIC (in shares)	1,079,130	1,071,441	1,065,866
DILUTED (in shares)	1,079,130	1,071,441	1,065,866