Fresh Start Accounting (Fresh Start - Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Apr. 30, 2021	Dec. 31, 2020
Predecessor [Member]
Current assets:
Cash and cash equivalents			$ 1,829
Total current assets			2,654
Property, plant and equipment, net		$ 13,020	12,931
Total assets			16,795
LIABILITIES AND EQUITY (DEFICIT)
Long-term debt due within one year		15	5,781
Accounts payable			540
Accrued other taxes			204
Other current liabilities			318
Total current liabilities			7,140
Deferred income taxes			343
Other liabilities			452
Long-term debt		6,738	5,820
Total liabilities not subject to compromise			10,130
Liabilities subject to compromise			11,565
Total liabilities			21,695
Equity (Deficit):
Common stock			27
Additional paid-in capital
Retained earnings (deficit)			(8,975)
Accumulated other comprehensive income (loss), net of tax			(755)
Treasury common stock			14
Total equity (deficit)			(4,900)
Total liabilities and equity (deficit)			16,795
Successor [Member]
Current assets:
Cash and cash equivalents	2,127	890
Accounts receivable, net		516
Contract acquisition costs
Prepaid expenses		92
Income taxes and other current assets		42
Total current assets	2,688	1,540
Property, plant and equipment, net	9,199	8,547
Other intangibles, net		4,441
Other assets		398
Total assets	16,481	14,926
LIABILITIES AND EQUITY (DEFICIT)
Long-term debt due within one year	15	15
Accounts payable	535	512
Advanced billings		208
Accrued other taxes	183	185
Accrued interest		80
Pension and other postretirement benefits		48
Other current liabilities	399	326
Total current liabilities	1,451	1,374
Deferred income taxes	387	291
Pension and other postretirement benefits		1,726
Other liabilities	403	412
Long-term debt	7,996	7,015
Total liabilities not subject to compromise	11,881	10,818
Liabilities subject to compromise
Total liabilities	11,881	10,818
Equity (Deficit):
Common stock	2	2
Additional paid-in capital		4,106
Retained earnings (deficit)	414
Accumulated other comprehensive income (loss), net of tax	60
Treasury common stock
Total equity (deficit)	4,600	4,108
Total liabilities and equity (deficit)	$ 16,481	14,926
Predecessor [Member] | Predecessor [Member]
Current assets:
Cash and cash equivalents		2,059
Accounts receivable, net		516
Contract acquisition costs		91
Prepaid expenses		92
Income taxes and other current assets		45
Total current assets		2,803
Property, plant and equipment, net		13,020
Other intangibles, net		578
Other assets		526
Total assets		16,927
LIABILITIES AND EQUITY (DEFICIT)
Long-term debt due within one year		5,782
Accounts payable		518
Advanced billings		208
Accrued other taxes		185
Accrued interest		81
Pension and other postretirement benefits		48
Other current liabilities		309
Total current liabilities		7,131
Deferred income taxes		389
Pension and other postretirement benefits		2,163
Other liabilities		440
Long-term debt
Total liabilities not subject to compromise		10,123
Liabilities subject to compromise		11,570
Total liabilities		21,693
Equity (Deficit):
Common stock		27
Additional paid-in capital		4,818
Retained earnings (deficit)		(8,855)
Accumulated other comprehensive income (loss), net of tax		(741)
Treasury common stock		(15)
Total equity (deficit)		(4,766)
Total liabilities and equity (deficit)		16,927
Predecessor [Member] | Successor [Member]
Equity (Deficit):
Common stock
Additional paid-in capital
Reorganization Adjustments [Member]
Current assets:
Cash and cash equivalents		(1,169)
Accounts receivable, net
Contract acquisition costs
Prepaid expenses
Income taxes and other current assets
Total current assets		(1,169)
Property, plant and equipment, net
Other intangibles, net
Other assets		(8)
Total assets		(1,177)
LIABILITIES AND EQUITY (DEFICIT)
Long-term debt due within one year		(5,767)
Accounts payable		(6)
Advanced billings
Accrued other taxes
Accrued interest		(1)
Pension and other postretirement benefits
Other current liabilities		53
Total current liabilities		(5,721)
Deferred income taxes		70
Pension and other postretirement benefits
Other liabilities
Long-term debt		6,738
Total liabilities not subject to compromise		1,087
Liabilities subject to compromise		(11,570)
Total liabilities		(10,483)
Equity (Deficit):
Retained earnings (deficit)		10,028
Accumulated other comprehensive income (loss), net of tax
Treasury common stock		15
Total equity (deficit)		9,306
Total liabilities and equity (deficit)		(1,177)
Reorganization Adjustments [Member] | Predecessor [Member]
Equity (Deficit):
Common stock		(27)
Additional paid-in capital		(4,818)
Reorganization Adjustments [Member] | Successor [Member]
Current assets:
Cash and cash equivalents		(1,169)
LIABILITIES AND EQUITY (DEFICIT)
Liabilities subject to compromise		11,570
Equity (Deficit):
Common stock		2
Additional paid-in capital		4,106
Retained earnings (deficit)		10,028
Fresh Start Adjustments [Member]
Current assets:
Cash and cash equivalents
Accounts receivable, net
Contract acquisition costs		(91)
Prepaid expenses
Income taxes and other current assets		(3)
Total current assets		(94)
Property, plant and equipment, net		(4,473)
Other intangibles, net		3,863
Other assets		(120)
Total assets		(824)
LIABILITIES AND EQUITY (DEFICIT)
Long-term debt due within one year
Accounts payable
Advanced billings
Accrued other taxes
Accrued interest
Pension and other postretirement benefits
Other current liabilities		(36)
Total current liabilities		(36)
Deferred income taxes		(168)
Pension and other postretirement benefits		(437)
Other liabilities		(28)
Long-term debt		277
Total liabilities not subject to compromise		(392)
Liabilities subject to compromise
Total liabilities		(392)
Equity (Deficit):
Retained earnings (deficit)		(1,173)
Accumulated other comprehensive income (loss), net of tax		741
Treasury common stock
Total equity (deficit)		(432)
Total liabilities and equity (deficit)		(824)
Fresh Start Adjustments [Member] | Predecessor [Member]
Equity (Deficit):
Common stock
Additional paid-in capital
Fresh Start Adjustments [Member] | Successor [Member]
Equity (Deficit):
Common stock
Additional paid-in capital