CONSOLIDATED STATEMENT OF CHANGES IN EQUITY - USD ($) $ in Millions		Common Stock [Member]	Preferred Stock [Member] Series B Preferred Stock [Member]	Additional Paid-In Capital [Member] Series B Preferred Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings (Accumulated Deficit) [Member]	[1]	Accumulated Other Comprehensive Income (Loss) [Member]	Common Stock in Treasury [Member]	Series B Preferred Stock [Member]	Total
Balance, shares at Dec. 31, 2014		354,488,992
Balance at Dec. 31, 2014		$ 4			$ 1,019	$ 3,577		$ 62			$ 4,662
Comprehensive loss:
Net income (loss)						(4,556)					(4,556)
Other comprehensive income (loss)								(110)			(110)
Comprehensive income (loss)											(4,666)
Stock-based compensation					48						48
Preferred stock dividend						(106)					(106)
Issuance of stock, shares		30,000,000	1,725,000
Issuance of stock				$ 1,673	669					$ 1,673	669
Issuance of restricted stock, shares		5,821,125
Cancellation of restricted stock, shares		(103,162)
Treasury stock - non-qualified plan									$ (1)		(1)
Tax withholding - stock compensation, shares		(73,869)
Issuance of stock awards, shares		5,463
Non-controlling interest						3					3
Balance, shares at Dec. 31, 2015		390,138,549	1,725,000
Balance at Dec. 31, 2015		$ 4			3,409	(1,082)		(48)	(1)		2,282
Comprehensive loss:
Net income (loss)						(2,643)					(2,643)
Other comprehensive income (loss)								9			9
Comprehensive income (loss)											(2,634)
Stock-based compensation					58						58
Preferred stock dividend, shares		7,166,389
Preferred stock dividend					(27)						(27)
Exercise of stock options, shares		44,880
Issuance of stock, shares		98,900,000
Issuance of stock		$ 1			1,246						1,247
Issuance of restricted stock, shares		87,472
Cancellation of restricted stock, shares		(165,483)
Tax withholding - stock compensation, shares		(929,252)
Tax withholding - stock compensation					(9)						(9)
Issuance of stock awards, shares		5,814
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 loss:
Net income (loss)						1,046					1,046	[2]
Other comprehensive income (loss)								(5)			(5)
Comprehensive income (loss)	[2]										1,041
Stock-based compensation					38						38
Preferred stock dividend, shares		12,791,716
Preferred stock dividend					(16)						(16)
Issuance of restricted stock, shares		5,055,208
Cancellation of restricted stock, shares		(742,028)
Performance units vested, shares		121,208
Tax withholding - stock compensation, shares		(340,234)
Tax withholding - stock compensation					(1)						(1)
Issuance of stock awards, shares		(72)
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

[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 2016-09 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 2017, deferred tax activity incurred in other comprehensive income was offset by a valuation allowance.