CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
OPERATING REVENUE	$ 5,167	$ 5,350	$ 15,587	$ 16,152
OPERATING EXPENSES
Cost of services and products (exclusive of depreciation and amortization)	2,236	2,334	6,703	6,877
Selling, general and administrative	850	831	2,598	2,723
Depreciation and amortization	1,193	1,235	3,515	3,619
Goodwill impairment	0	0	0	6,506
Total operating expenses	4,279	4,400	12,816	19,725
OPERATING INCOME (LOSS)	888	950	2,771	(3,573)
OTHER (EXPENSE) INCOME
Interest expense	(409)	(496)	(1,272)	(1,537)
Other income (loss), net	1	(44)	(73)	(5)
Total other expense, net	(408)	(540)	(1,345)	(1,542)
INCOME (LOSS) BEFORE INCOME TAXES	480	410	1,426	(5,115)
Income tax expense	114	108	369	377
NET INCOME (LOSS)	$ 366	$ 302	$ 1,057	$ (5,492)
BASIC AND DILUTED EARNINGS (LOSS) PER COMMON SHARE
BASIC (in dollars per share)	$ 0.34	$ 0.28	$ 0.98	$ (5.13)
DILUTED (in dollars per share)	$ 0.34	$ 0.28	$ 0.98	$ (5.13)
WEIGHTED-AVERAGE COMMON SHARES OUTSTANDING
BASIC (in shares)	1,080,505	1,072,543	1,078,672	1,070,921
DILUTED (in shares)	1,085,666	1,074,790	1,083,368	1,070,921