CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015
Cash Flows From Operating Activities:
Net income (loss)	$ 1,046	[1]	$ (2,643)	$ (4,556)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization	504		436	1,092
Impairment of natural gas and oil properties	0		2,321	6,950
Amortization of debt issuance costs	9		14	53
Deferred income taxes	(71)		(22)	(2,003)
(Gain) loss on derivatives, unsettled	(451)		373	155
Stock-based compensation	24		29	26
Gain on sale of assets, net	(6)			(283)
Restructuring charges			30
Loss on early extinguishment of debt	70		51
Other	13		8	34
Change in assets and liabilities:
Accounts receivable	(65)		(30)	203
Accounts payable	48		(69)	(78)
Taxes payable	4		(5)	(28)
Interest payable	(2)			9
Other assets and liabilities	(26)		5	6
Net cash provided by operating activities	1,097		498	1,580
Cash Flows From Investing Activities:
Capital investments	(1,268)		(593)	(1,798)
Acquisitions				(579)
Proceeds from sale of property and equipment	10		430	729
Other	6		1	10
Net cash used in investing activities	(1,252)		(162)	(1,638)
Cash Flows From Financing Activities:
Payments on current portion of long-term debt	(328)		(1)	(1)
Payments on long-term debt	(1,139)		(1,175)	(500)
Payments on short-term debt				(4,500)
Payments on revolving credit facility			(3,268)	(3,024)
Borrowings under revolving credit facility			3,152	2,840
Payments on commercial paper			(242)	(7,988)
Borrowings under commercial paper			242	7,988
Change in bank drafts outstanding	9		(20)	12
Proceeds from issuance of long-term debt	1,150		1,191	2,950
Payment of debt issuance costs	(24)		(17)	(20)
Proceeds from issuance of common stock			1,247	669
Proceeds from issuance of mandatory convertible preferred stock				1,673
Preferred stock dividend	(16)		(27)	(79)
Cash paid for tax withholding	(2)		(9)
Other	(2)		(1)
Net cash provided by (used in) financing activities	(352)		1,072	20
Increase (decrease) in cash and cash equivalents	(507)		1,408	(38)
Cash and cash equivalents at beginning of year	1,423		15	53
Cash and cash equivalents at end of year	$ 916		$ 1,423	$ 15

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