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:
Net income (loss)	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)
Performance units vested (in shares)		535,802
Treasury stock (in shares)						5,260,687
Treasury stock	(21)					$ (21)
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)
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)
Comprehensive loss:
Net income (loss)	(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
Performance units vested (in shares)		0
Treasury stock (in shares)	5,260,687
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)