Condensed Combined Debtors' Financial Information (Details) (USD $) In Millions, unless otherwise specified	0 Months Ended	3 Months Ended									12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011		Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income Statement:
Operating revenues		$ 280	$ 340	$ 324	$ 343	$ 381		$ 437	$ 400	$ 435	$ 1,287	$ 1,653	$ 1,788
Operating expenses											(1,615)	(2,351)	(1,594)
Reorganization items	(43)										(43)	0	0
Benefit for income taxes											(160)	441	16
Net Income (Loss)		(561)	(162)	(104)	(82)	(1,060)	[1]	33	(32)	(20)	(909)	(1,079)	163
Other comprehensive income (loss), net of tax
Other comprehensive loss, net of tax											(44)	(63)	(109)
Comprehensive Loss											(969)	(1,141)	55
Assets:
Total current assets	1,323	1,323				1,941					1,323	1,941
Investments in Unconsolidated Affiliates	534	534				523					534	523
Property, Plant and Equipment, less accumulated depreciation	4,516	4,516				4,472					4,516	4,472
Total other assets	128	128				222					128	222
Total Assets	7,520	7,520				8,323					7,520	8,323
Property, Plant and Equipment, accumulated depreciation (in dollars)	1,431	1,431				1,295					1,431	1,295
Liabilities and Shareholders' Equity:
Total current liabilities	820	820				548					820	548
Liabilities subject to compromise	3,959	3,959				0					3,959	0
Deferred taxes	81	81				0					81	0
Other long-term liabilities	528	528				627					528	627
Total Liabilities	6,788	6,788				6,659					6,788	6,659
Total equity	732	732				1,664					732	1,664	2,821	2,837
Total Liabilities and Equity	7,520	7,520				8,323					7,520	8,323
Net Cash (used in) provided by:
Operating activities											(513)	626	606
Financing activities											564	277	235
Investing activities											(461)	(678)	(562)
Net decrease in cash and cash equivalents											(333)	273	268
Cash and cash equivalents at beginning of period from continuing operations					1,221					948	1,221	948	680
Cash and cash equivalents at end of period from continuing operations	888	888				1,221					888	1,221	948
Debtor Entities
Income Statement:
Operating revenues											901
Operating expenses											(1,262)
Other expenses											(226)
Reorganization items											(43)
Benefit for income taxes											(153)
Net loss attributable to debtor entities											(783)
Equity in loss of non-debtor entities, net of tax											(142)
Net Income (Loss)											(925)
Other comprehensive income (loss), net of tax
Other comprehensive loss, net of tax											(44)
Comprehensive Loss											(969)
Assets:
Total current assets	633	633									633
Investments in Unconsolidated Affiliates	152	152									152
Property, Plant and Equipment, less accumulated depreciation	1,428	1,428									1,428
Investment in non-debtor entities	1,983	1,983									1,983
Total other assets	976	976									976
Total Assets	5,172	5,172									5,172
Property, Plant and Equipment, accumulated depreciation (in dollars)	845	845									845
Liabilities and Shareholders' Equity:
Total current liabilities	93	93									93
Liabilities subject to compromise	3,959	3,959									3,959
Deferred taxes	131	131									131
Other long-term liabilities	257	257									257
Total Liabilities	4,440	4,440									4,440
Total equity	732	732									732
Total Liabilities and Equity	5,172	5,172									5,172
Net Cash (used in) provided by:
Operating activities											(596)
Financing activities											173
Investing activities											(109)
Net decrease in cash and cash equivalents											(532)
Cash and cash equivalents at beginning of period from continuing operations					955						955
Cash and cash equivalents at end of period from continuing operations	423	423									423
Cash paid for reorganization items											$ 20

[1] Reflects $704 million pre-tax ($424 million after tax) of asset impairment charges. For more information, see Note 13—Asset Impairments and Other Charges. In addition, the amount reflects a $1,032 million pre-tax ($623 million after tax) impairment charge related to Homer City. For more information, see Note 14—Discontinued Operations.