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Reportable Segments (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017 | Dec. 31, 2017
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Operating Revenue |  | $ 1,599 |  | $ 1,527 | $ 5,044 |  | $ 4,805 |
Net income (loss) available to common stockholders |  | 169 |  | 172 | 549 |  | 463 |
Plant, property, and equipment, gross |  | 23,751 |  |  | 23,751 |  |  | $ 22,506
Total Assets |  | 23,913 |  |  | 23,913 |  |  | 23,050
Consumers Energy Company |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Operating Revenue |  | 1,502 |  | 1,437 | 4,752 |  | 4,536 |
Net income (loss) available to common stockholder |  | 180 |  | 181 | 573 |  | 495 |
Plant, property, and equipment, gross |  | 23,322 |  |  | 23,322 |  |  | 22,318
Total Assets |  | 21,492 |  |  | 21,492 |  |  | 21,099
Operating Segments | Electric Utility |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Operating Revenue |  | 1,313 |  | 1,247 | 3,480 |  | 3,360 |
Net income (loss) available to common stockholders |  | 199 |  | 176 | 468 |  | 394 |
Plant, property, and equipment, gross | [1] | 15,772 |  |  | 15,772 |  |  | 15,221
Total Assets | [1] | 13,850 |  |  | 13,850 |  |  | 13,906
Operating Segments | Electric Utility | Consumers Energy Company |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Operating Revenue |  | 1,313 |  | 1,247 | 3,480 |  | 3,360 |
Net income (loss) available to common stockholder |  | 199 |  | 176 | 468 |  | 394 |
Plant, property, and equipment, gross | [1] | 15,772 |  |  | 15,772 |  |  | 15,221
Total Assets | [1] | 13,914 |  |  | 13,914 |  |  | 13,907
Operating Segments | Gas Utility |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Operating Revenue |  | 189 |  | 190 | 1,272 |  | 1,176 |
Net income (loss) available to common stockholders |  | (19) |  | 5 | 105 |  | 101 |
Plant, property, and equipment, gross | [1] | 7,534 |  |  | 7,534 |  |  | 7,080
Total Assets | [1] | 7,513 |  |  | 7,513 |  |  | 7,139
Operating Segments | Gas Utility | Consumers Energy Company |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Operating Revenue |  | 189 |  | 190 | 1,272 |  | 1,176 |
Net income (loss) available to common stockholder |  | (19) |  | 5 | 105 |  | 101 |
Plant, property, and equipment, gross | [1] | 7,534 |  |  | 7,534 |  |  | 7,080
Total Assets | [1] | 7,556 |  |  | 7,556 |  |  | 7,139
Operating Segments | Enterprises |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Operating Revenue |  | 57 | [2] | 58 | 181 | [2] | 172 |
Net income (loss) available to common stockholders |  | 4 |  | 8 | 33 |  | 27 |
Plant, property, and equipment, gross |  | 405 |  |  | 405 |  |  | 167
Total Assets |  | 538 |  |  | 538 |  |  | 342
Other reconciling items |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Operating Revenue |  | 40 | [3] | 32 | 111 | [3] | 97 |
Net income (loss) available to common stockholders |  | (15) |  | $ (17) | (57) |  | $ (59) |
Plant, property, and equipment, gross |  | 40 |  |  | 40 |  |  | 38
Total Assets |  | 2,012 |  |  | 2,012 |  |  | 1,663
Other reconciling items | Consumers Energy Company |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |
Operating Revenue |  | 0 |  |  | 0 |  |  |
Plant, property, and equipment, gross |  | 16 |  |  | 16 |  |  | 17
Total Assets |  | $ 22 |  |  | $ 22 |  |  | $ 53
[1] | Amounts include a portion of Consumers’ other common assets attributable to both the electric and gas utility businesses.
[2] | Amounts represent the enterprises segment’s operating revenue from independent power production and CMS ERM’s sales of energy commodities in support of the independent power production portfolio.
[3] | Amount represents EnerBank’s operating revenue from unsecured consumer installment loans for financing home improvements.

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