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Significant Accounting Policies (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2015 | Dec. 31, 2014
EnerBank [Member] |  |
Significant Accounting Policies [Line Items] |  |
Unearned income | $ 82 | $ 62
Minimum [Member] | EnerBank [Member] |  |
Significant Accounting Policies [Line Items] |  |
Same as cash, fee recognition period | 3 months |
Authorized contractor, fee recognition period | 1 year |
Maximum [Member] | Consumers Energy Company [Member] |  |
Significant Accounting Policies [Line Items] |  |
Financial incentive as percentage of energy optimization program spending | 15.00% |
Energy optimization spending limit | 2.00% |
Maximum [Member] | EnerBank [Member] |  |
Significant Accounting Policies [Line Items] |  |
Same as cash, fee recognition period | 24 months |
Authorized contractor, fee recognition period | 12 years |

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- Definition The limit, as a percentage of retail revenue, of energy optimization program spending. + References No definition available. + Details
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- Definition Amount of deferred interest and fee income, unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of acquired loans. Excludes amounts for loans and leases covered under loss sharing agreements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 20 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6378556&loc=d3e10152-111534 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5074-111524 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.7) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 30 -Section 50 -Paragraph 4 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=25496975&loc=d3e45377-112738 + Details
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