Regulatory Matters (Details) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Mar. 31, 2011	Mar. 31, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2009
Detroit Edison's PSCR reconciliation filing currently pending with the MPSC
Under recovery	$ (52,600,000)		$ 52,600,000
Over recovery		15,600,000	15,600,000
PSCR Cost of Power Sold	1,200,000,000	1,200,000,000
MichCon's GCR reconciliation filing currently pending with the MPSC
Net over - recovery of GCR expense			1,000,000	5,900,000
GCR Cost of Gas Sold			700,000,000	1,000,000,000
Regulatory Matters (Textuals) [Abstract]
Over recovery		15,600,000	15,600,000
Under recovery	(52,600,000)		52,600,000
Under recovery for pension equalization mechanism			7,100,000
Over recovery on refund for self implemented rates			3,800,000
Power supply cost recovery expense forecast for next year			1,200,000,000
Recovery of the amount as part of the 2010 PSCR reconciliation			36,000,000
Power supply cost recovery plan case factor 2011			2.98 mills/kWh
MichCon GCR Plan Case Factor 2010 to 2011					5.89 Per Mcf
2011-2012 GCR plan case factor			5.89 per MCF GCR Plan Case Factor
Requested increase in revenue required to recover cost associated with regulatory matters			443,000,000
Proposed adjustments which could reduce the requested increase			190,000,000
Refund for Choice Implementation Surcharge			2,400,000
New composite depreciation rates			3.06%
Detroit Edison's Current Composite Rate			3.33%
Additional revenue			100,000,000
Self implemented rates increase			107,000,000
Restoration and line clearance refund			16,000,000
Revenue Decoupling Mechanism Refund			$ 55,800,000