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Retirement Benefits (Tables) | 6 Months Ended
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Jun. 30, 2015
Defined Benefit Plan Disclosure [Line Items] |
Schedule Of Net Benefit Costs |
In Millions
| DB Pension Plan |  | OPEB Plan |
| Three Months Ended |  | Six Months Ended |  | Three Months Ended |  | Six Months Ended |
June 30 | 2015 | 2014 |  | 2015 | 2014 |  | 2015 | 2014 |  | 2015 | 2014 |
CMS Energy, including Consumers |
Net periodic cost (credit) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Service cost |  | $ | 12 |  | $ | 10 |  |  | $ | 24 |  | $ | 20 |  |  | $ | 6 |  | $ | 5 |  |  | $ | 12 |  | $ | 10 |
Interest expense |  |  | 26 |  |  | 25 |  |  |  | 51 |  |  | 50 |  |  |  | 14 |  |  | 14 |  |  |  | 29 |  |  | 28 |
Expected return on plan assets |  |  | (35) |  |  | (34) |  |  |  | (69) |  |  | (68) |  |  |  | (22) |  |  | (22) |  |  |  | (45) |  |  | (44) |
Amortization of: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net loss |  |  | 22 |  |  | 14 |  |  |  | 45 |  |  | 29 |  |  |  | 6 |  |  | 1 |  |  |  | 11 |  |  | 1 |
Prior service cost (credit) |  |  | 1 |  |  | 1 |  |  |  | 1 |  |  | 1 |  |  |  | (11) |  |  | (11) |  |  |  | (21) |  |  | (21) |
Net periodic cost (credit) |  | $ | 26 |  | $ | 16 |  |  | $ | 52 |  | $ | 32 |  |  | $ | (7) |  | $ | (13) |  |  | $ | (14) |  | $ | (26) |
Consumers |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net periodic cost (credit) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Service cost |  | $ | 12 |  | $ | 10 |  |  | $ | 24 |  | $ | 20 |  |  | $ | 6 |  | $ | 5 |  |  | $ | 12 |  | $ | 10 |
Interest expense |  |  | 24 |  |  | 24 |  |  |  | 49 |  |  | 48 |  |  |  | 14 |  |  | 14 |  |  |  | 28 |  |  | 27 |
Expected return on plan assets |  |  | (34) |  |  | (33) |  |  |  | (67) |  |  | (66) |  |  |  | (21) |  |  | (21) |  |  |  | (43) |  |  | (42) |
Amortization of: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net loss |  |  | 22 |  |  | 14 |  |  |  | 44 |  |  | 28 |  |  |  | 5 |  |  | 1 |  |  |  | 11 |  |  | 2 |
Prior service cost (credit) |  |  | 1 |  |  | 1 |  |  |  | 1 |  |  | 1 |  |  |  | (10) |  |  | (10) |  |  |  | (20) |  |  | (20) |
Net periodic cost (credit) |  | $ | 25 |  | $ | 16 |  |  | $ | 51 |  | $ | 31 |  |  | $ | (6) |  | $ | (11) |  |  | $ | (12) |  | $ | (23) |
Consumers Energy Company [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Schedule Of Net Benefit Costs |
In Millions
| DB Pension Plan |  | OPEB Plan |
| Three Months Ended |  | Six Months Ended |  | Three Months Ended |  | Six Months Ended |
June 30 | 2015 | 2014 |  | 2015 | 2014 |  | 2015 | 2014 |  | 2015 | 2014 |
CMS Energy, including Consumers |
Net periodic cost (credit) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Service cost |  | $ | 12 |  | $ | 10 |  |  | $ | 24 |  | $ | 20 |  |  | $ | 6 |  | $ | 5 |  |  | $ | 12 |  | $ | 10 |
Interest expense |  |  | 26 |  |  | 25 |  |  |  | 51 |  |  | 50 |  |  |  | 14 |  |  | 14 |  |  |  | 29 |  |  | 28 |
Expected return on plan assets |  |  | (35) |  |  | (34) |  |  |  | (69) |  |  | (68) |  |  |  | (22) |  |  | (22) |  |  |  | (45) |  |  | (44) |
Amortization of: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net loss |  |  | 22 |  |  | 14 |  |  |  | 45 |  |  | 29 |  |  |  | 6 |  |  | 1 |  |  |  | 11 |  |  | 1 |
Prior service cost (credit) |  |  | 1 |  |  | 1 |  |  |  | 1 |  |  | 1 |  |  |  | (11) |  |  | (11) |  |  |  | (21) |  |  | (21) |
Net periodic cost (credit) |  | $ | 26 |  | $ | 16 |  |  | $ | 52 |  | $ | 32 |  |  | $ | (7) |  | $ | (13) |  |  | $ | (14) |  | $ | (26) |
Consumers |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net periodic cost (credit) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Service cost |  | $ | 12 |  | $ | 10 |  |  | $ | 24 |  | $ | 20 |  |  | $ | 6 |  | $ | 5 |  |  | $ | 12 |  | $ | 10 |
Interest expense |  |  | 24 |  |  | 24 |  |  |  | 49 |  |  | 48 |  |  |  | 14 |  |  | 14 |  |  |  | 28 |  |  | 27 |
Expected return on plan assets |  |  | (34) |  |  | (33) |  |  |  | (67) |  |  | (66) |  |  |  | (21) |  |  | (21) |  |  |  | (43) |  |  | (42) |
Amortization of: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net loss |  |  | 22 |  |  | 14 |  |  |  | 44 |  |  | 28 |  |  |  | 5 |  |  | 1 |  |  |  | 11 |  |  | 2 |
Prior service cost (credit) |  |  | 1 |  |  | 1 |  |  |  | 1 |  |  | 1 |  |  |  | (10) |  |  | (10) |  |  |  | (20) |  |  | (20) |
Net periodic cost (credit) |  | $ | 25 |  | $ | 16 |  |  | $ | 51 |  | $ | 31 |  |  | $ | (6) |  | $ | (11) |  |  | $ | (12) |  | $ | (23) |

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- Definition Tabular disclosure of the components of net benefit costs for pension plans and/or other employee benefit plans including service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) recognized due to settlements or curtailments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 + Details
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