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Reportable Segments (Details) - USD ($) $ in Millions | 3 Months Ended |
--- | --- | ---
Mar. 31, 2018 | Mar. 31, 2017 | Dec. 31, 2017
Segment Reporting Information [Line Items] |  |  |  |
Operating Revenue |  | $ 1,953 | $ 1,829 |
Net income available to common stockholders |  | 241 | 199 |
Plant, property, and equipment, gross |  | 22,878 |  | $ 22,506
Total Assets |  | 22,868 |  | 23,050
Consumers Energy Company [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Operating Revenue |  | 1,855 | 1,737 |
Net income available to common stockholders |  | 242 | 211 |
Plant, property, and equipment, gross |  | 22,692 |  | 22,318
Total Assets |  | 20,949 |  | 21,099
Electric Utility [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Operating Revenue |  | 1,078 | 1,036 |
Net income available to common stockholders |  | 139 | 124 |
Plant, property, and equipment, gross | [1] | 15,432 |  | 15,221
Total Assets | [1] | 13,986 |  | 13,906
Electric Utility [Member] | Consumers Energy Company [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Operating Revenue |  | 1,078 | 1,036 |
Net income available to common stockholders |  | 139 | 124 |
Plant, property, and equipment, gross | [1] | 15,432 |  | 15,221
Total Assets | [1] | 13,986 |  | 13,907
Gas Utility [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Operating Revenue |  | 777 | 701 |
Net income available to common stockholders |  | 103 | 87 |
Plant, property, and equipment, gross | [1] | 7,244 |  | 7,080
Total Assets | [1] | 6,941 |  | 7,139
Gas Utility [Member] | Consumers Energy Company [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Operating Revenue |  | 777 | 701 |
Net income available to common stockholders |  | 103 | 87 |
Plant, property, and equipment, gross | [1] | 7,244 |  | 7,080
Total Assets | [1] | 6,941 |  | 7,139
Enterprises [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Operating Revenue |  | 63 | 59 |
Net income available to common stockholders |  | 15 | 12 |
Plant, property, and equipment, gross |  | 165 |  | 167
Total Assets |  | 348 |  | 342
Other reconciling items [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Operating Revenue |  | 35 | 33 |
Net income available to common stockholders |  | (16) | $ (24) |
Plant, property, and equipment, gross |  | 37 |  | 38
Total Assets |  | 1,593 |  | 1,663
Other reconciling items [Member] | Consumers Energy Company [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Plant, property, and equipment, gross |  | 16 |  | 17
Total Assets |  | $ 22 |  | $ 53
[1] | Amounts include a portion of Consumers' other common assets attributable to both the electric and gas utility businesses.

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