Regulatory Matters (Schedule of the Components of PSCR and GCR Over/(Under) Recoveries) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Accrued gas revenue	$ 27us-gaap_DeferredFuelCost
Accrued rate refunds	6cms_AccruedRateRefunds	12cms_AccruedRateRefunds
Consumers Energy Company [Member]
Accrued gas revenue	27
Accrued rate refunds	$ 6	$ 12

Carrying amount as of the balance sheet date of capitalized fuel costs of a regulated entity that are expected to be recoverable through rate adjustments within one year or the normal operating cycle, if longer.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 340

-Section 25

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6499739&loc=d3e43603-110378

Name:	us-gaap_DeferredFuelCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant