CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Millions		Total		Common Stock	Preferred Stock	Additional Paid-in Capital	Accumulated Deficit	[1]	Accumulated Other Comprehensive Income (Loss)	Common Stock in Treasury
Beginning balance (in shares) at Dec. 31, 2016				495,248,369	1,725,000					31,269
Beginning balance at Dec. 31, 2016		$ 917		$ 5		$ 4,677	$ (3,725)		$ (39)	$ (1)
Comprehensive income:
Net income		1,046	[2]				1,046
Other comprehensive loss		(5)							(5)
Comprehensive income	[2]	1,041
Stock-based compensation		38				38
Preferred stock dividend (in shares)				12,791,716
Preferred stock dividend		(16)				(16)
Issuance of restricted stock (in shares)				5,055,208
Cancellation of restricted stock (in shares)				(742,028)
Performance units vested (in shares)				121,208
Issuance of common stock (in shares)				72
Tax withholding - stock compensation (in shares)				(340,234)
Tax withholding - stock compensation		(1)				(1)
Ending balance (in shares) at Dec. 31, 2017				512,134,311	1,725,000					31,269
Ending balance at Dec. 31, 2017		1,979		$ 5		4,698	(2,679)		(44)	$ (1)
Comprehensive income:
Net income		537	[2]				537
Other comprehensive loss		8							8
Comprehensive income	[2]	545
Stock-based compensation		$ 21				21
Conversion of preferred stock (in shares)				74,998,614	(1,725,000)
Conversion of preferred stock				$ 1		(1)
Issuance of restricted stock (in shares)				349,562
Cancellation of restricted stock (in shares)				(1,804,122)
Treasury stock (in shares)		39,061,268								39,061,268
Treasury stock		$ (180)								$ (180)
Performance units vested (in shares)				214,866
Tax withholding - stock compensation (in shares)				(486,124)
Tax withholding - stock compensation		(3)				(3)
Ending balance (in shares) at Dec. 31, 2018				585,407,107	0					39,092,537
Ending balance at Dec. 31, 2018		2,362		$ 6		4,715	(2,142)		(36)	$ (181)
Comprehensive income:
Net income		891					891
Other comprehensive loss		3							3
Comprehensive income		894
Stock-based compensation		$ 12				12
Issuance of restricted stock (in shares)				236,978
Cancellation of restricted stock (in shares)				(239,571)
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)				(384,393)
Tax withholding - stock compensation		(1)				(1)
Ending balance (in shares) at Dec. 31, 2019				585,555,923	0					44,353,224
Ending balance at Dec. 31, 2019		$ 3,246		$ 6		$ 4,726	$ (1,251)		$ (33)	$ (202)

[1] Includes a net cumulative-effect adjustment of $59 million related to the recognition of previously unrecognized windfall tax benefits resulting from the adoption of ASU 2016-9 as of the beginning of 2017. This adjustment increased net deferred tax assets and the related income tax valuation allowance by the same amount.

[2] In 2018 and 2017, deferred tax activity incurred in other comprehensive income was offset by a valuation allowance.