The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4H

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624258-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 44D

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_DerivativeNetLiabilityPositionAggregateFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Derivative Instruments (Narrative) (Details) (USD $) In Millions, unless otherwise specified			3 Months Ended		9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 Financial Transmission Right [Member] Consumers Energy Company [Member]	Sep. 30, 2011 Financial Transmission Right [Member] Consumers Energy Company [Member]	Sep. 30, 2012 Financial Transmission Right [Member] Consumers Energy Company [Member]	Sep. 30, 2011 Financial Transmission Right [Member] Consumers Energy Company [Member]	Sep. 30, 2012 Other Assets [Member] Commodity Contracts [Member]	Dec. 31, 2011 Other Assets [Member] Commodity Contracts [Member]	Sep. 30, 2012 Other Assets [Member] Commodity Contracts [Member] Consumers Energy Company [Member]	Dec. 31, 2011 Other Assets [Member] Commodity Contracts [Member] Consumers Energy Company [Member]	Sep. 30, 2012 Other Liabilities [Member] Commodity Contracts [Member]	Dec. 31, 2011 Other Liabilities [Member] Commodity Contracts [Member]
Derivative assets							$ 6	$ 3	$ 4	$ 2
Derivative liabilities											6	7
Gain or loss deferred in regulatory accounts			1	(1)	8	1
Derivative liabilities subject to credit-related-contingent features	$ 4	$ 4