Fair Value Measurements (Assets And Liabilties Measured At Fair Value On A Recurring Basis) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 87	$ 53
Restricted cash equivalents	16	14
Nonqualified deferred compensation plan assets	6	5
Commodity contracts	5	3
Total	250	203
Nonqualified deferred compensation plan liabilities	6	5
Commodity contracts	1	4
Total	7	9
Consumers Energy Company [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted cash equivalents	15	13
Nonqualified deferred compensation plan assets	4	4
Commodity contracts	4	2
Total	147	137
Nonqualified deferred compensation plan liabilities	4	4
Total	4	4
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	87	53
Restricted cash equivalents	16	14
Nonqualified deferred compensation plan assets	6	5
Total	245	200
Nonqualified deferred compensation plan liabilities	6	5
Total	6	5
Fair Value, Inputs, Level 1 [Member] | Consumers Energy Company [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted cash equivalents	15	13
Nonqualified deferred compensation plan assets	4	4
Total	143	135
Nonqualified deferred compensation plan liabilities	4	4
Total	4	4
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity contracts	1
Total	1
Commodity contracts	1	3
Total	1	3
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity contracts	4	3
Total	4	3
Commodity contracts		1
Total		1
Fair Value, Inputs, Level 3 [Member] | Consumers Energy Company [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commodity contracts	4	2
Total	4	2
DB SERP [Member] | Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale - Fair Value		2
DB SERP [Member] | Cash Equivalents [Member] | Consumers Energy Company [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale - Fair Value		1
DB SERP [Member] | Mutual Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale - Fair Value	136	126
DB SERP [Member] | Mutual Fund [Member] | Consumers Energy Company [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale - Fair Value	95	85
DB SERP [Member] | Fair Value, Inputs, Level 1 [Member] | Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale - Fair Value		2
DB SERP [Member] | Fair Value, Inputs, Level 1 [Member] | Cash Equivalents [Member] | Consumers Energy Company [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale - Fair Value		1
DB SERP [Member] | Fair Value, Inputs, Level 1 [Member] | Mutual Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale - Fair Value	136	126
DB SERP [Member] | Fair Value, Inputs, Level 1 [Member] | Mutual Fund [Member] | Consumers Energy Company [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale - Fair Value	95	85
CMS Energy Common Stock [Member] | Consumers Energy Company [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale - Fair Value	29	32
CMS Energy Common Stock [Member] | Fair Value, Inputs, Level 1 [Member] | Consumers Energy Company [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale - Fair Value	$ 29	$ 32