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Stock-Based Compensation (Narrative) (Details) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 USD ($) shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Deferred compensation arrangements plan term | 10 years
Number of shares authorized (in shares) | 6,500,000
Maximum shares issuable per employee (in shares) | 500,000
Shares available for grant (in shares) | 3,258,000
Consumers Energy Company |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Deferred compensation arrangements plan term | 10 years
Number of shares authorized (in shares) | 6,500,000.0
Maximum shares issuable per employee (in shares) | 500,000
Shares available for grant (in shares) | 3,714,544
Minimum |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Percent of initial grant issued on vesting date | 0.00%
Minimum | Consumers Energy Company |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Percent of initial grant issued on vesting date | 0.00%
Maximum |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Percent of initial grant issued on vesting date | 200.00%
Maximum | Consumers Energy Company |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Percent of initial grant issued on vesting date | 200.00%
Performance-based awards |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Service period | 38 months
Vesting period | 3 years
Performance-based awards | Consumers Energy Company |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Service period | 38 months
Vesting period | 3 years
Performance-based awards | Minimum |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Service period | 36 months
Performance-based awards | Minimum | Consumers Energy Company |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Service period | 36 months
Market-based awards |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Service period | 3 years
Vesting period | 3 years
Market-based awards | Consumers Energy Company |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Service period | 3 years
Vesting period | 3 years
Time-lapse awards |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Service period | 3 years
Time-lapse awards | Consumers Energy Company |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Service period | 3 years
Restricted stock units |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Service period | 1 year
Shares forfeited (in shares) | 0
Restricted stock units | Consumers Energy Company |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Service period | 1 year
Shares forfeited (in shares) | 0
Restricted stock |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Shares forfeited (in shares) | 46,949
Unrecognized compensation cost | $ | $ 21.7
Unrecognized compensation cost recognition period | 2 years
Restricted stock | Consumers Energy Company |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Shares forfeited (in shares) | 40,139
Unrecognized compensation cost | $ | $ 20.8
Unrecognized compensation cost recognition period | 2 years

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