CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Millions	Total	COMMON STOCK	ADDITIONAL PAID-IN CAPITAL	ACCUMULATED OTHER COMPREHENSIVE LOSS	ACCUMULATED OTHER COMPREHENSIVE LOSS Cumulative Effect, Period of Adoption, Adjustment	RETAINED EARNINGS (ACCUMULATED DEFICIT)	RETAINED EARNINGS (ACCUMULATED DEFICIT) Cumulative Effect, Period of Adoption, Adjustment
Balance at beginning of period at Dec. 31, 2017		$ 1,069	$ 23,314	$ (1,995)		$ 1,103
Balance at beginning of period (Accounting Standards Update 2014-09) at Dec. 31, 2017							$ 338
Balance at beginning of period (Accounting Standards Update 2018-02) at Dec. 31, 2017					$ (407)		407
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201602Member
Issuance of common stock through dividend reinvestment, incentive and benefit plans		11
Issuance of common stock to acquire Level 3, including replacement of Level 3's share-based compensation awards			(2)
Shares withheld to satisfy tax withholdings			(56)
Share-based compensation and other, net			187
Dividends declared			(586)			(1,758)
Acquisition of additional minority interest in a subsidiary			(5)
Net loss	$ (1,733)					(1,733)
Other comprehensive loss	(59)			(59)
Balance at end of period at Dec. 31, 2018	$ 19,828	1,080	22,852	(2,461)		(1,643)	96
Increase (Decrease) in Stockholders' Equity [Roll Forward]
DIVIDENDS DECLARED PER COMMON SHARE (in dollars per share)	$ 2.16
Income Tax Expense (Benefit)	$ (170)					(37)
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Issuance of common stock through dividend reinvestment, incentive and benefit plans		10
Issuance of common stock to acquire Level 3, including replacement of Level 3's share-based compensation awards			0
Shares withheld to satisfy tax withholdings			(37)
Share-based compensation and other, net			163
Dividends declared			(1,104)			2
Acquisition of additional minority interest in a subsidiary			0
Net loss	$ (5,269)					(5,269)
Other comprehensive loss	(219)			(219)
Balance at end of period at Dec. 31, 2019	$ 13,470	1,090	21,874	(2,680)		(6,814)	$ 9
Increase (Decrease) in Stockholders' Equity [Roll Forward]
DIVIDENDS DECLARED PER COMMON SHARE (in dollars per share)	$ 1.00
Income Tax Expense (Benefit)	$ (503)					2
Issuance of common stock through dividend reinvestment, incentive and benefit plans		7
Issuance of common stock to acquire Level 3, including replacement of Level 3's share-based compensation awards			0
Shares withheld to satisfy tax withholdings			(40)
Share-based compensation and other, net			187
Dividends declared			(1,112)			6
Acquisition of additional minority interest in a subsidiary			0
Net loss	(1,232)					(1,232)
Other comprehensive loss	(133)			(133)
Balance at end of period at Dec. 31, 2020	$ 11,162	$ 1,097	$ 20,909	$ (2,813)		$ (8,031)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
DIVIDENDS DECLARED PER COMMON SHARE (in dollars per share)	$ 1.00
Income Tax Expense (Benefit)	$ (450)