Contingencies And Commitments (Contingencies And Commitments) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended									1 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Oct. 31, 2010	Jun. 30, 2013 Consumers Energy Company [Member]	Dec. 31, 2012 Consumers Energy Company [Member]	Jun. 30, 2013 NREPA [Member] Consumers Energy Company [Member]	Jun. 30, 2013 Superfund Liability [Member] Consumers Energy Company [Member]	Jun. 30, 2013 Manufactured Gas Plant [Member] Consumers Energy Company [Member] item	Dec. 31, 2011 Big Rock Decommissioning [Member] Consumers Energy Company [Member]	Jul. 31, 2011 DOE Settlement [Member] Consumers Energy Company [Member]
Demand for payment by USEPA			$ 7
Cumulative environmental charge	228
Accrual for environmental loss contingencies	58					4	2	121
Discounted projected costs rate	4.34%							2.57%
Accrual for environmental loss contingencies, inflation rate	1.00%							2.50%
Remaining undiscounted obligation amount	77							130
Foreign government tax claim on sale	142
Remediation and other response activity costs, minimum						4	2
Remediation and other response activity costs. maximum						6	8
Litigation settlement, gross										120
Number of former MGPs								23
Regulatory assets, noncurrent	$ 2,202	$ 2,287		$ 2,202	$ 2,287			$ 151	$ 85