Contingencies And Commitments (Expected Remediation Cost By Year) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014
Manufactured Gas Plant [Member] | Consumers Energy Company [Member]
Site Contingency [Line Items]
Undiscounted amount due within one year	$ 7
Undiscounted amount due within two year	14
Undiscounted amount due within third year	12
Undiscounted amount due within fourth year	10
Undiscounted amount due within five year	19
Bay Harbor [Member]
Site Contingency [Line Items]
Undiscounted amount due within one year	8
Undiscounted amount due within two year	6
Undiscounted amount due within third year	6
Undiscounted amount due within fourth year	5
Undiscounted amount due within five year	$ 5