CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Millions	Total	COMMON STOCK	ADDITIONAL PAID-IN CAPITAL	ACCUMULATED OTHER COMPREHENSIVE LOSS	RETAINED EARNINGS (ACCUMULATED DEFICIT)
Balance at beginning of period at Dec. 31, 2015		$ 544	$ 15,178	$ (1,934)	$ 272
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	$ 626				626
Issuance of common stock to acquire Level 3, including replacement of Level 3's share-based compensation awards		0	0
Issuance of common stock through dividend reinvestment, incentive and benefit plans		3	7
Shares withheld to satisfy tax withholdings			(15)
Share-based compensation and other, net			79
Acquisition of additional minority interest in a subsidiary			0
Other comprehensive (loss) income	(183)			(183)
Dividends declared			(279)		(899)
Balance at end of period at Dec. 31, 2016	$ 13,399	547	14,970	(2,117)	(1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
DIVIDENDS DECLARED PER COMMON SHARE (usd per share)	$ 2.16
Cumulative effect of adoption | Accounting Standards Update 2018-02				0	0
Cumulative effect of adoption | Accounting Standards Update 2014-09					0
Cumulative effect of adoption | Accounting Standards Update 2016-09					0
Net (loss) income	$ 1,389				1,389
Issuance of common stock to acquire Level 3, including replacement of Level 3's share-based compensation awards		517	9,462
Issuance of common stock through dividend reinvestment, incentive and benefit plans		5	0
Shares withheld to satisfy tax withholdings			(20)
Share-based compensation and other, net			79
Acquisition of additional minority interest in a subsidiary			0
Other comprehensive (loss) income	122			122
Dividends declared			(1,177)		(288)
Balance at end of period at Dec. 31, 2017	$ 23,491	1,069	23,314	(1,995)	1,103
Increase (Decrease) in Stockholders' Equity [Roll Forward]
DIVIDENDS DECLARED PER COMMON SHARE (usd per share)	$ 2.16
Cumulative effect of adoption | Accounting Standards Update 2018-02				0	0
Cumulative effect of adoption | Accounting Standards Update 2014-09					0
Cumulative effect of adoption | Accounting Standards Update 2016-09					3
Net (loss) income	$ (1,733)				(1,733)
Issuance of common stock to acquire Level 3, including replacement of Level 3's share-based compensation awards		0	(2)
Issuance of common stock through dividend reinvestment, incentive and benefit plans		11	0
Shares withheld to satisfy tax withholdings			(56)
Share-based compensation and other, net			187
Acquisition of additional minority interest in a subsidiary			(5)
Other comprehensive (loss) income	(59)			(59)
Dividends declared			(586)		(1,758)
Balance at end of period at Dec. 31, 2018	$ 19,828	$ 1,080	$ 22,852	(2,461)	(1,643)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
DIVIDENDS DECLARED PER COMMON SHARE (usd per share)	$ 2.16
Cumulative effect of adoption | Accounting Standards Update 2018-02				$ (407)	407
Cumulative effect of adoption | Accounting Standards Update 2014-09					338
Cumulative effect of adoption | Accounting Standards Update 2016-09					$ 0