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		10	(9)
Shares withheld to satisfy tax withholdings			(35)
Share-based compensation and other, net			90
Dividends declared					(1,174)
Other comprehensive income	$ (89)			(89)
Net (loss) income	407				407
Balance at end of period at Jun. 30, 2018	$ 22,988	1,079	23,360	(2,491)	1,040
Increase (Decrease) in Stockholders' Equity
DIVIDENDS DECLARED PER COMMON SHARE (in dollars per share)	$ 1.08
Balance at beginning of period at Mar. 31, 2018		1,079	23,316	(2,288)	1,336
Increase (Decrease) in Stockholders' Equity
Issuance of common stock through dividend reinvestment, incentive and benefit plans			(3)
Shares withheld to satisfy tax withholdings			(10)
Share-based compensation and other, net			57
Dividends declared					(588)
Other comprehensive income	$ (203)			(203)
Net (loss) income	292				292
Balance at end of period at Jun. 30, 2018	$ 22,988	1,079	23,360	(2,491)	1,040
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	(14)
Shares withheld to satisfy tax withholdings			(29)
Share-based compensation and other, net			77
Dividends declared			(544)		1
Other comprehensive income	42			42
Net (loss) income	(5,794)				(5,794)
Balance at end of period at Jun. 30, 2019	$ 13,692	1,090	22,342	(2,419)	(7,321)
Increase (Decrease) in Stockholders' Equity
DIVIDENDS DECLARED PER COMMON SHARE (in dollars per share)	$ 0.50
Balance at beginning of period at Mar. 31, 2019		1,090	22,575	(2,429)	(7,693)
Increase (Decrease) in Stockholders' Equity
Issuance of common stock through dividend reinvestment, incentive and benefit plans			(2)
Shares withheld to satisfy tax withholdings			(3)
Share-based compensation and other, net			44
Dividends declared			(272)		1
Other comprehensive income	$ 10			10
Net (loss) income	371				371
Balance at end of period at Jun. 30, 2019	$ 13,692	$ 1,090	$ 22,342	$ (2,419)	$ (7,321)
Increase (Decrease) in Stockholders' Equity
DIVIDENDS DECLARED PER COMMON SHARE (in dollars per share)	$ 0.25