CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Millions	Common Stock Outstanding [Member]	Preferred Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Common Stock in Treasury [Member]	Total
Balance, shares at Dec. 31, 2016	495,248,369	1,725,000
Balance at Dec. 31, 2016	$ 5		$ 4,677	$ (3,725)	$ (39)	$ (1)	$ 917
Comprehensive income:
Net income (loss)				351			351
Comprehensive income							351
Stock-based compensation			10				10
Preferred stock dividend, shares	2,751,410
Issuance of restricted stock, shares	4,549,122
Cancellation of restricted stock, shares	(113,185)
Performance units vested, shares	121,208
Tax withholding - stock compensation, shares	(59,455)
Balance, shares at Mar. 31, 2017	502,497,469	1,725,000
Balance at Mar. 31, 2017	$ 5		4,687	(3,374)	(39)	(1)	1,278
Balance, shares at Dec. 31, 2016	495,248,369	1,725,000
Balance at Dec. 31, 2016	$ 5		4,677	(3,725)	(39)	(1)	917
Comprehensive income:
Net income (loss)							712
Other comprehensive income							2
Comprehensive income							$ 714
Preferred stock dividend, shares							10,040,306
Balance, shares at Sep. 30, 2017	509,142,659	1,725,000
Balance at Sep. 30, 2017	$ 5		4,698	(3,013)	(37)	(1)	$ 1,652
Balance, shares at Mar. 31, 2017	502,497,469	1,725,000
Balance at Mar. 31, 2017	$ 5		4,687	(3,374)	(39)	(1)	1,278
Comprehensive income:
Net income (loss)				284			284
Other comprehensive income					1		1
Comprehensive income							285
Stock-based compensation			10				10
Preferred stock dividend, shares	3,346,865
Issuance of restricted stock, shares	353,803
Cancellation of restricted stock, shares	(303,135)
Tax withholding - stock compensation, shares	(1,729)
Issuance of stock awards, shares	72
Balance, shares at Jun. 30, 2017	505,893,345	1,725,000
Balance at Jun. 30, 2017	$ 5		4,697	(3,090)	(38)	(1)	1,573
Comprehensive income:
Net income (loss)				77			77
Other comprehensive income					1		1
Comprehensive income							78
Stock-based compensation			9				9
Preferred stock dividend, shares	3,346,738
Preferred stock dividend			(8)				(8)
Issuance of restricted stock, shares	133,197
Cancellation of restricted stock, shares	(192,810)
Tax withholding - stock compensation, shares	(37,811)
Balance, shares at Sep. 30, 2017	509,142,659	1,725,000
Balance at Sep. 30, 2017	$ 5		4,698	(3,013)	(37)	(1)	1,652
Balance, shares at Dec. 31, 2017	512,134,311	1,725,000
Balance at Dec. 31, 2017	$ 5		4,698	(2,679)	(44)	(1)	1,979
Comprehensive income:
Net income (loss)				208			208
Comprehensive income							208
Stock-based compensation			7				7
Conversion of preferred stock, shares	74,998,614	(1,725,000)
Conversion of preferred stock	$ 1		(1)
Issuance of restricted stock, shares	5,076
Cancellation of restricted stock, shares	(160,168)
Performance units vested, shares	214,866
Tax withholding - stock compensation, shares	(338,808)
Tax withholding - stock compensation			(1)				(1)
Balance, shares at Mar. 31, 2018	586,853,891
Balance at Mar. 31, 2018	$ 6		4,703	(2,471)	(44)	(1)	2,193
Balance, shares at Dec. 31, 2017	512,134,311	1,725,000
Balance at Dec. 31, 2017	$ 5		4,698	(2,679)	(44)	(1)	1,979
Comprehensive income:
Net income (loss)							230
Other comprehensive income							4
Comprehensive income							234
Balance, shares at Sep. 30, 2018	586,195,162
Balance at Sep. 30, 2018	$ 6		4,714	(2,449)	(40)	(26)	2,205
Balance, shares at Mar. 31, 2018	586,853,891
Balance at Mar. 31, 2018	$ 6		4,703	(2,471)	(44)	(1)	2,193
Comprehensive income:
Net income (loss)				51			51
Comprehensive income							51
Stock-based compensation			6				6
Issuance of restricted stock, shares	307,743
Cancellation of restricted stock, shares	(722,465)
Tax withholding - stock compensation, shares	(9,068)
Balance, shares at Jun. 30, 2018	586,430,101
Balance at Jun. 30, 2018	$ 6		4,709	(2,420)	(44)	(1)	2,250
Comprehensive income:
Net income (loss)				(29)			(29)
Other comprehensive income					4		4
Comprehensive income							(25)
Stock-based compensation			5				5
Issuance of restricted stock, shares	30,924
Cancellation of restricted stock, shares	(248,342)
Treasury stock						(25)	(25)
Tax withholding - stock compensation, shares	(17,521)
Balance, shares at Sep. 30, 2018	586,195,162
Balance at Sep. 30, 2018	$ 6		$ 4,714	$ (2,449)	$ (40)	$ (26)	$ 2,205