CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Millions	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Common Stock in Treasury
Balance (in shares) at Dec. 31, 2018		585,407,107				39,092,537
Balance beginning at Dec. 31, 2018	$ 2,362	$ 6	$ 4,715	$ (2,142)	$ (36)	$ (181)
Comprehensive (loss) income:
Net (loss) income	594			594
Comprehensive income (loss)	594
Stock-based compensation	$ 3		3
Issuance of restricted stock (in shares)		8,798
Cancellation of restricted stock (in shares)		(128,324)
Treasury stock (in shares)	5,260,687					5,260,687
Treasury stock	$ (21)					$ (21)
Performance units vested (in shares)		535,802
Tax withholding - stock compensation (in shares)		(274,657)
Tax withholding – stock compensation	(1)		(1)
Balance (in shares) at Mar. 31, 2019		585,548,726				44,353,224
Balance ending at Mar. 31, 2019	2,937	$ 6	4,717	(1,548)	(36)	$ (202)
Balance (in shares) at Dec. 31, 2018		585,407,107				39,092,537
Balance beginning at Dec. 31, 2018	2,362	$ 6	4,715	(2,142)	(36)	$ (181)
Comprehensive (loss) income:
Net (loss) income	781
Comprehensive income (loss)	786
Balance (in shares) at Sep. 30, 2019		585,637,420				44,353,224
Balance ending at Sep. 30, 2019	3,135	$ 6	4,723	(1,361)	(31)	$ (202)
Balance (in shares) at Dec. 31, 2018		585,407,107				39,092,537
Balance beginning at Dec. 31, 2018	2,362	$ 6	4,715	(2,142)	(36)	$ (181)
Balance (in shares) at Dec. 31, 2019		585,555,923				44,353,224
Balance ending at Dec. 31, 2019	3,246	$ 6	4,726	(1,251)	(33)	$ (202)
Balance (in shares) at Mar. 31, 2019		585,548,726				44,353,224
Balance beginning at Mar. 31, 2019	2,937	$ 6	4,717	(1,548)	(36)	$ (202)
Comprehensive (loss) income:
Net (loss) income	138			138
Other comprehensive income	4				4
Comprehensive income (loss)	142
Stock-based compensation	3		3
Issuance of restricted stock (in shares)		6,424
Cancellation of restricted stock (in shares)		(72,555)
Tax withholding - stock compensation (in shares)		(4,250)
Balance (in shares) at Jun. 30, 2019		585,478,345				44,353,224
Balance ending at Jun. 30, 2019	3,082	$ 6	4,720	(1,410)	(32)	$ (202)
Comprehensive (loss) income:
Net (loss) income	49			49
Other comprehensive income	1				1
Comprehensive income (loss)	50
Stock-based compensation	3		3
Issuance of restricted stock (in shares)		205,883
Cancellation of restricted stock (in shares)		(33,851)
Tax withholding - stock compensation (in shares)		(12,957)
Balance (in shares) at Sep. 30, 2019		585,637,420				44,353,224
Balance ending at Sep. 30, 2019	3,135	$ 6	4,723	(1,361)	(31)	$ (202)
Balance (in shares) at Dec. 31, 2019		585,555,923				44,353,224
Balance beginning at Dec. 31, 2019	3,246	$ 6	4,726	(1,251)	(33)	$ (202)
Comprehensive (loss) income:
Net (loss) income	(1,547)			(1,547)
Comprehensive income (loss)	(1,547)
Stock-based compensation	1		1
Issuance of restricted stock (in shares)		12,397
Cancellation of restricted stock (in shares)		(167,130)
Restricted units granted (in shares)		1,005,976
Restricted units granted	1		1
Tax withholding - stock compensation (in shares)		(383,731)
Balance (in shares) at Mar. 31, 2020		586,023,435				44,353,224
Balance ending at Mar. 31, 2020	1,701	$ 6	4,728	(2,798)	(33)	$ (202)
Balance (in shares) at Dec. 31, 2019		585,555,923				44,353,224
Balance beginning at Dec. 31, 2019	3,246	$ 6	4,726	(1,251)	(33)	$ (202)
Comprehensive (loss) income:
Net (loss) income	(3,020)
Other comprehensive income					1
Comprehensive income (loss)	(3,019)
Balance (in shares) at Sep. 30, 2020		649,899,653				44,353,224
Balance ending at Sep. 30, 2020	384	$ 7	4,882	(4,271)	(32)	$ (202)
Balance (in shares) at Mar. 31, 2020		586,023,435				44,353,224
Balance beginning at Mar. 31, 2020	1,701	$ 6	4,728	(2,798)	(33)	$ (202)
Comprehensive (loss) income:
Net (loss) income	(880)			(880)
Comprehensive income (loss)	(880)
Stock-based compensation	1		1
Issuance of restricted stock (in shares)		222,489
Cancellation of restricted stock (in shares)		(1,079,515)
Restricted units granted (in shares)		1,649,294
Restricted units granted	2		2
Tax withholding - stock compensation (in shares)		(222,163)
Tax withholding – stock compensation	(1)		(1)
Balance (in shares) at Jun. 30, 2020		586,593,540				44,353,224
Balance ending at Jun. 30, 2020	823	$ 6	4,730	(3,678)	(33)	$ (202)
Comprehensive (loss) income:
Net (loss) income	(593)			(593)
Other comprehensive income	1				1
Comprehensive income (loss)	(592)
Stock-based compensation	1		1
Issuance of common stock (in shares)		63,250,000
Issuance of common stock	152	$ 1	151
Issuance of restricted stock (in shares)		63,344
Cancellation of restricted stock (in shares)		(5,196)
Tax withholding - stock compensation (in shares)		(2,035)
Balance (in shares) at Sep. 30, 2020		649,899,653				44,353,224
Balance ending at Sep. 30, 2020	$ 384	$ 7	$ 4,882	$ (4,271)	$ (32)	$ (202)