Supplemental Cash Flows Information (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Cash paid (received)
Interest (net of amount capitalized)	$ 168	[1]	$ 290	[1]	$ 239	[1]
Income taxes	59		(216)		(96)
Cash payments under plant operating leases	199		311		325
Details of assets acquired
Fair value of assets acquired	0		1		1
Liabilities assumed	0		0		0
Net assets acquired	0		1		1
Non-cash activities from consolidation of VIEs
Assets	0		0		94
Liabilities	0		0		99
Non-cash activities from deconsolidation of variable interest entities
Assets	0		0		249
Liabilities	0		0		253
Non-cash activities from vendor financing	11		21		190
Interest paid	199		317		293
Interest capitalized	31		27		54
Accrued capital expenditures	31		29		58
Edison International
Non-cash activities from deconsolidation of variable interest entities
Non-cash distribution to parent	222		0		0
Midwest Generation LLC
Cash paid (received)
Interest (net of amount capitalized)	36		43		51
Income taxes	0		8		136
Non-cash activities from deconsolidation of variable interest entities
Accrued capital expenditures	9		4		16
Edison Mission Energy | Midwest Generation LLC
Non-cash activities from deconsolidation of variable interest entities
Non-cash distribution to parent	$ 106		$ 0		$ 0

[1] Interest paid by EME for December 31, 2012, 2011 and 2010 was $199 million, $317 million and $293 million, respectively. Interest capitalized by EME for December 31, 2012, 2011 and 2010 was $31 million, $27 million and $54 million, respectively.