Financial Instruments (Schedule Of Investment Securities) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Investment Securities [Line Items]
Held to maturity securities - Cost	$ 12	$ 10
Held to maturity securities - Fair Value	12	10
Debt Securities [Member]
Investment Securities [Line Items]
Held to maturity securities - Cost	12	10
Held to maturity securities - Unrealized Losses
Held to maturity securities - Fair Value	12	10
CMS Energy Common Stock [Member] \| Consumers Energy Company [Member]
Investment Securities [Line Items]
Available for sale - Cost	5	5
Available for sale - Unrealized Gains	29	24
Available for sale - Unrealized Losses
Available for sale - Fair Value	34	29
DB SERP [Member] \| Mutual Fund [Member]
Investment Securities [Line Items]
Available for sale - Cost	133	136
Available for sale - Unrealized Gains	1
Available for sale - Unrealized Losses
Available for sale - Fair Value	134	136
DB SERP [Member] \| Mutual Fund [Member] \| Consumers Energy Company [Member]
Investment Securities [Line Items]
Available for sale - Cost	94	95
Available for sale - Unrealized Gains	1
Available for sale - Unrealized Losses
Available for sale - Fair Value	$ 95	$ 95

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This item represents the cost of equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments for other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

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- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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- Definition

Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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Amount of accumulated unrealized loss on investments in debt securities classified as held-to-maturity.

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Fair value of investments in debt securities classified as held-to-maturity.

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