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, 2017		$ 1,069	$ 23,314	$ (1,995)	$ 1,103
Increase (Decrease) in Stockholders' Equity
Issuance of common stock through dividend reinvestment, incentive and benefit plans		12	(2)
Shares withheld to satisfy tax withholdings			(50)
Share-based compensation and other, net			137
Dividends declared					(1,758)
Other comprehensive (loss) income	$ (53)			(53)
Net (loss) income	679				679
Balance at end of period at Sep. 30, 2018	$ 22,802	1,081	23,399	(2,455)	777
Increase (Decrease) in Stockholders' Equity
DIVIDENDS DECLARED PER COMMON SHARE (in dollars per share)	$ 1.62
Balance at beginning of period at Jun. 30, 2018		1,079	23,360	(2,491)	1,040
Increase (Decrease) in Stockholders' Equity
Issuance of common stock through dividend reinvestment, incentive and benefit plans		2	7
Shares withheld to satisfy tax withholdings			(15)
Share-based compensation and other, net			47
Dividends declared					(584)
Other comprehensive (loss) income	$ 36			36
Net (loss) income	272				272
Balance at end of period at Sep. 30, 2018	$ 22,802	1,081	23,399	(2,455)	777
Increase (Decrease) in Stockholders' Equity
DIVIDENDS DECLARED PER COMMON SHARE (in dollars per share)	$ 0.54
Balance at beginning of period at Dec. 31, 2018	$ 19,828	1,080	22,852	(2,461)	(1,643)
Increase (Decrease) in Stockholders' Equity
Issuance of common stock through dividend reinvestment, incentive and benefit plans		10	(15)
Shares withheld to satisfy tax withholdings			(35)
Share-based compensation and other, net			115
Dividends declared			(816)		2
Other comprehensive (loss) income	(38)			(38)
Net (loss) income	(5,492)				(5,492)
Balance at end of period at Sep. 30, 2019	$ 13,674	1,090	22,101	(2,499)	(7,018)
Increase (Decrease) in Stockholders' Equity
DIVIDENDS DECLARED PER COMMON SHARE (in dollars per share)	$ 0.75
Balance at beginning of period at Jun. 30, 2019		1,090	22,342	(2,419)	(7,321)
Increase (Decrease) in Stockholders' Equity
Issuance of common stock through dividend reinvestment, incentive and benefit plans			(1)
Shares withheld to satisfy tax withholdings			(6)
Share-based compensation and other, net			38
Dividends declared			(272)		1
Other comprehensive (loss) income	$ (80)			(80)
Net (loss) income	302				302
Balance at end of period at Sep. 30, 2019	$ 13,674	$ 1,090	$ 22,101	$ (2,499)	$ (7,018)
Increase (Decrease) in Stockholders' Equity
DIVIDENDS DECLARED PER COMMON SHARE (in dollars per share)	$ 0.25