Consolidated Statements Of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows provided from (used by) operating activities:
Net loss	$ (402)	$ (5,911)	$ (643)
Adjustments to reconcile net loss to net cash provided from (used by) operating activities:
Depreciation and amortization	1,598	1,780	1,954
(Gain) Loss on early extinguishment of debt	72	20	(32)
Pension settlement costs	159	57	41
Pension/OPEB special termination benefit enhancements		44
Stock-based compensation expense	3	15	18
Amortization of deferred financing costs	15	30	34
Non-cash reorganization items	93
Other adjustments	6		(32)
Deferred income taxes	(91)	(619)	(67)
Goodwill impairment		5,725	641
Loss on disposal of Northwest Operations	162	446
Change in accounts receivable	73	48	65
Change in accounts payable and other liabilities	342	(122)	(141)
Change in prepaid expenses, income taxes and other assets	(41)	(5)	(26)
Net cash provided from operating activities	1,989	1,508	1,812
Cash flows provided from (used by) investing activities:
Capital expenditures - Business operations	(1,181)	(1,226)	(1,192)
Proceeds from sale of Northwest Operations	1,131
Proceeds on sale of assets	27	88	11
Other	4	4	5
Net cash used by investing activities	(19)	(1,134)	(1,176)
Cash flows provided from (used by) financing activities:
Long-term debt payments	(4,948)	(2,008)	(2,515)
Proceeds from long-term debt borrowings	4,950	1,650	1,840
Proceeds from revolving debt		949	525
Repayment of revolving debt	(749)	(475)	(250)
Financing costs paid	(121)	(44)	(43)
Dividends paid on preferred stock			(107)
Premium paid to retire debt			(17)
Finance lease obligation payments	(23)	(35)	(36)
Other	(2)	(5)	(5)
Net cash provided from (used by) financing activities	(893)	32	(608)
Increase (Decrease) in cash, cash equivalents and restricted cash	1,077	406	28
Cash, cash equivalents and restricted cash at January 1,	810	404	376
Cash, cash equivalents and restricted cash at December 31,	1,887	810	404
Cash paid (received) during the period for:
Interest	612	1,469	1,507
Income tax payments, net	8	4	4
Reorganization items, net	270
Non-cash investing and financing activities:
Financing obligation for contributions of real property to pension plan			37
Reduction of pension obligation			$ 37
Increase (Decrease) in capital expenditures due to changes in accounts payable	$ (117)	$ 13