CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016
Cash Flows From Operating Activities:
Net income (loss)	$ 537	$ 1,046	[1]	$ (2,643)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization	560	504		436
Amortization of debt issuance costs	8	9		14
Impairments	171			2,321
Deferred income taxes		(71)		(22)
(Gain) loss on derivatives, unsettled	24	(451)		373
Stock-based compensation	14	24		29
Gain on sale of assets, net	(17)	(6)
Restructuring charges				30
Loss on early extinguishment of debt	17	70		51
Other	(1)	13		8
Change in assets and liabilities:
Accounts receivable	(153)	(65)		(30)
Accounts payable	65	48		(69)
Taxes payable	2	4		(5)
Interest payable	(10)	(2)
Other assets and liabilities	6	(26)		5
Net cash provided by operating activities	1,223	1,097		498
Cash Flows From Investing Activities:
Capital investments	(1,290)	(1,268)		(593)
Proceeds from sale of property and equipment	1,643	10		430
Other	6	6		1
Net cash provided by (used in) investing activities	359	(1,252)		(162)
Cash Flows From Financing Activities:
Payments on current portion of long-term debt		(328)		(1)
Payments on long-term debt	(2,095)	(1,139)		(1,175)
Payments on revolving credit facility	(1,983)			(3,268)
Borrowings under revolving credit facility	1,983			3,152
Payments on commercial paper				(242)
Borrowings under commercial paper				242
Change in bank drafts outstanding	17	9		(20)
Proceeds from issuance of long-term debt		1,150		1,191
Debt issuance costs	(9)	(24)		(17)
Proceeds from issuance of common stock				1,247
Purchase of treasury stock	(180)
Preferred stock dividend	(27)	(16)		(27)
Cash paid for tax withholding	(3)	(2)		(9)
Other		(2)		(1)
Net cash (used in) provided by financing activities	(2,297)	(352)		1,072
Increase (decrease) in cash and cash equivalents	(715)	(507)		1,408
Cash and cash equivalents at beginning of year	916	1,423		15
Cash and cash equivalents at end of year	$ 201	$ 916		$ 1,423

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