Leases (Schedule of Rent Expense) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Leases [Line Items]
Contingent rental expense	$ 77		$ 33		$ 11
Consumers Energy Company [Member]
Leases [Line Items]
Contingent rental expense	77	[1]	33	[1]	11	[1]
PPAs [Member]
Leases [Line Items]
Minimum operating lease expense	6		6		10
PPAs [Member] | Consumers Energy Company [Member]
Leases [Line Items]
Minimum operating lease expense	6		6		10
Non-PPAs [Member]
Leases [Line Items]
Minimum operating lease expense	21		23		22
Non-PPAs [Member] | Consumers Energy Company [Member]
Leases [Line Items]
Minimum operating lease expense	$ 21		$ 23		$ 22

[1] Contingent rental expense is related to capital and operating lease PPAs and is based on delivery of energy and capacity in excess of minimum lease payments.