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Financings and Capitalization (Summary of Long-Term Debt Outstanding) (Details) (USD $) |  |  |  |  |  |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  |  |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  |  |  | 12 Months Ended |  | 12 Months Ended |  |  |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  | 12 Months Ended |  |  |  |
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Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2012 Consumers Energy Company [Member] | Dec. 31, 2011 Consumers Energy Company [Member] | Dec. 31, 2012 CMS Energy [Member] | Dec. 31, 2011 CMS Energy [Member] | Dec. 31, 2012 Term Loan Facility Due December 2016 [Member] | Feb. 28, 2013 Term Loan Facility Due December 2016 [Member] | Dec. 31, 2012 Securitization Bonds [Member] Consumers Energy Company [Member] | Dec. 31, 2011 Securitization Bonds [Member] Consumers Energy Company [Member] | Dec. 31, 2012 Tax-Exempt Pollution Control Revenue Bonds [Member] Consumers Energy Company [Member] | Dec. 31, 2011 Tax-Exempt Pollution Control Revenue Bonds [Member] Consumers Energy Company [Member] | Dec. 31, 2012 Senior Notes [Member] | Dec. 31, 2011 Senior Notes [Member] | Dec. 31, 2012 Senior Notes [Member] Senior Notes Variable Rate Due January 2013 [Member] | Dec. 31, 2011 Senior Notes [Member] Senior Notes Variable Rate Due January 2013 [Member] | Dec. 31, 2012 Senior Notes [Member] Senior Notes 2.75% Due May 2014 [Member] | Dec. 31, 2011 Senior Notes [Member] Senior Notes 2.75% Due May 2014 [Member] | Dec. 31, 2012 Senior Notes [Member] Senior Notes 6.875% Due December 2015 [Member] | Dec. 31, 2011 Senior Notes [Member] Senior Notes 6.875% Due December 2015 [Member] | Dec. 31, 2012 Senior Notes [Member] Senior Notes 4.25% Due September 2015 [Member] | Dec. 31, 2011 Senior Notes [Member] Senior Notes 4.25% Due September 2015 [Member] | Dec. 31, 2012 Senior Notes [Member] Senior Notes 6.55% Due July 2017 [Member] | Dec. 31, 2011 Senior Notes [Member] Senior Notes 6.55% Due July 2017 [Member] | Dec. 31, 2012 Senior Notes [Member] Senior Notes 5.05% Due February 2018 [Member] | Dec. 31, 2011 Senior Notes [Member] Senior Notes 5.05% Due February 2018 [Member] | Dec. 31, 2012 Senior Notes [Member] Senior Notes 8.75% Due June 2019 [Member] | Dec. 31, 2011 Senior Notes [Member] Senior Notes 8.75% Due June 2019 [Member] | Dec. 31, 2012 Senior Notes [Member] Senior Notes 6.25% Due February 2020 [Member] | Dec. 31, 2011 Senior Notes [Member] Senior Notes 6.25% Due February 2020 [Member] | Dec. 31, 2012 Senior Notes [Member] Senior Notes 5.05% Due March 2022 [Member] | Dec. 31, 2012 Senior Notes [Member] 2.875% Convertible Senior Notes Due 2024 [Member] | Dec. 31, 2011 Senior Notes [Member] 2.875% Convertible Senior Notes Due 2024 [Member] | Dec. 31, 2012 Senior Notes [Member] Senior Notes 5.5% Due June 2029 [Member] | Dec. 31, 2011 Senior Notes [Member] Senior Notes 5.5% Due June 2029 [Member] | Dec. 31, 2012 Senior Notes [Member] Senior Notes 6.875% Due March 2018 [Member] Consumers Energy Company [Member] | Dec. 31, 2011 Senior Notes [Member] Senior Notes 6.875% Due March 2018 [Member] Consumers Energy Company [Member] | Dec. 31, 2012 Other CMS Subsidiaries [Member] | Dec. 31, 2011 Other CMS Subsidiaries [Member] | Dec. 31, 2012 Other CMS Subsidiaries [Member] Trust Preferred Securities [Member] | Dec. 31, 2011 Other CMS Subsidiaries [Member] Trust Preferred Securities [Member] | Dec. 31, 2012 Other CMS Subsidiaries [Member] EnerBank certificates of deposit [Member] | Dec. 31, 2011 Other CMS Subsidiaries [Member] EnerBank certificates of deposit [Member] | Dec. 31, 2012 First Mortgage Bonds [Member] Consumers Energy Company [Member] | Dec. 31, 2011 First Mortgage Bonds [Member] Consumers Energy Company [Member] | Dec. 31, 2012 First Mortgage Bonds [Member] FMBs 5% Due February 2012 [Member] Consumers Energy Company [Member] | Dec. 31, 2011 First Mortgage Bonds [Member] FMBs 5% Due February 2012 [Member] Consumers Energy Company [Member] | Dec. 31, 2012 First Mortgage Bonds [Member] FMBs 5.375% Due April 2013 [Member] Consumers Energy Company [Member] | Dec. 31, 2011 First Mortgage Bonds [Member] FMBs 5.375% Due April 2013 [Member] Consumers Energy Company [Member] | Dec. 31, 2012 First Mortgage Bonds [Member] FMBs 6% Due February 2014 [Member] Consumers Energy Company [Member] | Dec. 31, 2011 First Mortgage Bonds [Member] FMBs 6% Due February 2014 [Member] Consumers Energy Company [Member] | Dec. 31, 2012 First Mortgage Bonds [Member] FMBs 5% Due March 2015 [Member] Consumers Energy Company [Member] | Dec. 31, 2011 First Mortgage Bonds [Member] FMBs 5% Due March 2015 [Member] Consumers Energy Company [Member] | Dec. 31, 2012 First Mortgage Bonds [Member] FMBs 2.6% Due October 2015 [Member] Consumers Energy Company [Member] | Dec. 31, 2011 First Mortgage Bonds [Member] FMBs 2.6% Due October 2015 [Member] Consumers Energy Company [Member] | Dec. 31, 2012 First Mortgage Bonds [Member] FMBs 5.5% Due August 2016 [Member] Consumers Energy Company [Member] | Dec. 31, 2011 First Mortgage Bonds [Member] FMBs 5.5% Due August 2016 [Member] Consumers Energy Company [Member] | Dec. 31, 2012 First Mortgage Bonds [Member] FMBs 5.15% Due February 2017 [Member] Consumers Energy Company [Member] | Dec. 31, 2011 First Mortgage Bonds [Member] FMBs 5.15% Due February 2017 [Member] Consumers Energy Company [Member] | Dec. 31, 2012 First Mortgage Bonds [Member] FMBs 3.21% Due October 2017 [Member] Consumers Energy Company [Member] | Dec. 31, 2011 First Mortgage Bonds [Member] FMBs 3.21% Due October 2017 [Member] Consumers Energy Company [Member] | Dec. 31, 2012 First Mortgage Bonds [Member] FMBs 5.65% Due September 2018 [Member] Consumers Energy Company [Member] | Dec. 31, 2011 First Mortgage Bonds [Member] FMBs 5.65% Due September 2018 [Member] Consumers Energy Company [Member] | Dec. 31, 2012 First Mortgage Bonds [Member] FMBs 6.125% Due March 2019 [Member] Consumers Energy Company [Member] | Dec. 31, 2011 First Mortgage Bonds [Member] FMBs 6.125% Due March 2019 [Member] Consumers Energy Company [Member] | Dec. 31, 2012 First Mortgage Bonds [Member] FMBs 6.7% Due September 2019 [Member] Consumers Energy Company [Member] | Dec. 31, 2011 First Mortgage Bonds [Member] FMBs 6.7% Due September 2019 [Member] Consumers Energy Company [Member] | Dec. 31, 2012 First Mortgage Bonds [Member] FMBs 5.65% Due April 2020 [Member] Consumers Energy Company [Member] | Dec. 31, 2011 First Mortgage Bonds [Member] FMBs 5.65% Due April 2020 [Member] Consumers Energy Company [Member] | Dec. 31, 2012 First Mortgage Bonds [Member] FMBs 3.77% Due October 2020 [Member] Consumers Energy Company [Member] | Dec. 31, 2011 First Mortgage Bonds [Member] FMBs 3.77% Due October 2020 [Member] Consumers Energy Company [Member] | Dec. 31, 2012 First Mortgage Bonds [Member] FMBs 5.3% Due September 2022 [Member] Consumers Energy Company [Member] | Dec. 31, 2011 First Mortgage Bonds [Member] FMBs 5.3% Due September 2022 [Member] Consumers Energy Company [Member] | Dec. 31, 2012 First Mortgage Bonds [Member] First Mortgage Bonds 2.85% Due May 2022 [Member] Consumers Energy Company [Member] | Dec. 31, 2012 First Mortgage Bonds [Member] First Mortgage Bonds 3.19% Due 2024 [Member] Consumers Energy Company [Member] | Dec. 31, 2012 First Mortgage Bonds [Member] First Mortgage Bonds 3.39% Due 2027 [Member] Consumers Energy Company [Member] | Dec. 31, 2012 First Mortgage Bonds [Member] First Mortgage Bonds 4.31% Due 2042 [Member] Consumers Energy Company [Member] | Dec. 31, 2012 First Mortgage Bonds [Member] FMBs 5.8% Due September 2035 [Member] Consumers Energy Company [Member] | Dec. 31, 2011 First Mortgage Bonds [Member] FMBs 5.8% Due September 2035 [Member] Consumers Energy Company [Member] | Dec. 31, 2012 First Mortgage Bonds [Member] FMBs 6.17% Due September 2040 [Member] Consumers Energy Company [Member] | Dec. 31, 2011 First Mortgage Bonds [Member] FMBs 6.17% Due September 2040 [Member] Consumers Energy Company [Member] | Dec. 31, 2012 First Mortgage Bonds [Member] FMBs 4.97% Due October 2040 [Member] Consumers Energy Company [Member] | Dec. 31, 2011 First Mortgage Bonds [Member] FMBs 4.97% Due October 2040 [Member] Consumers Energy Company [Member] | Dec. 31, 2012 Debt Issuances [Member] | Dec. 31, 2012 Debt Issuances [Member] Consumers Energy Company [Member] | Dec. 31, 2012 Debt Issuances [Member] CMS Energy [Member] | Feb. 28, 2013 Debt Issuances [Member] Term Loan Facility Due December 2016 [Member] CMS Energy [Member] | Dec. 31, 2012 Debt Issuances [Member] Term Loan Facility Due December 2016 [Member] CMS Energy [Member] | Dec. 31, 2012 Debt Retirements [Member] Trust Preferred Securities [Member] CMS Energy [Member] | Dec. 31, 2012 Debt Retirements [Member] 2.875% Convertible Senior Notes Due 2024 [Member] CMS Energy [Member]
Interest rate |  |  |  |  |  |  |  |  | 5.718% | [1] |  |  |  |  |  |  |  | 2.75% |  | 6.875% |  | 4.25% |  | 6.55% |  | 5.05% |  | 8.75% |  | 6.25% |  | 5.05% | 2.875% | [2] |  | 5.50% | [2] |  | 6.875% |  |  |  | 7.75% | [3] |  | 1.164% | [4] |  |  |  |  |  | 5.00% | [5] |  |  | 5.375% | [5],[6] |  |  | 6.00% | [5] |  |  | 5.00% | [5] |  |  | 2.60% | [5] |  |  | 5.50% | [5] |  |  | 5.15% | [5] |  |  | 3.21% | [5] |  |  | 5.65% | [5] |  |  | 6.125% | [5] |  |  | 6.70% | [5] |  |  | 5.65% | [5] |  |  | 3.77% | [5] |  |  | 5.30% | [5] |  |  | 2.85% | [5] | 3.19% | [5] | 3.39% | [5] | 4.31% | [5] | 5.80% | [5] |  |  | 6.17% | [5] |  |  | 4.97% | [5] |  |  |  |  |  |  |  |  | 7.75% | 2.875% | [7]
Weighted-average interest rate |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1.16% |  | 1.33% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maturity Date |  |  |  |  |  |  | 2016 |  | 2013-2015 |  |  | 2018-2035 |  |  |  | 2013 |  | 2014 |  | 2015 |  | 2015 |  | 2017 |  | 2018 |  | 2019 |  | 2020 |  | 2022 | 2024 |  |  | 2029 |  |  | 2018 |  |  |  | 2027 |  |  | 2013-2020 |  |  |  |  |  |  | 2012 | [5] |  |  | 2013 | [5] |  |  | 2014 | [5] |  |  | 2015 | [5] |  |  | 2015 | [5] |  |  | 2016 | [5] |  |  | 2017 | [5] |  |  | 2017 | [5] |  |  | 2018 | [5] |  |  | 2019 | [5] |  |  | 2019 | [5] |  |  | 2020 | [5] |  |  | 2020 | [5] |  |  | 2022 | [5] |  |  | 2022 | [5] | 2024 | [5] | 2027 | [5] | 2042 | [5] | 2035 | [5] |  |  | 2040 | [5] |  |  | 2040 | [5] |  |  |  |  |  |  |  |  |  |  |
Principal Balance |  |  |  |  | $ 2,377,000,000 | $ 2,273,000,000 | $ 180,000,000 |  | $ 133,000,000 |  | $ 171,000,000 | $ 103,000,000 | $ 103,000,000 | $ 2,197,000,000 | $ 2,273,000,000 |  | $ 150,000,000 | $ 250,000,000 | $ 250,000,000 | $ 125,000,000 | $ 125,000,000 | $ 250,000,000 | $ 250,000,000 | $ 250,000,000 | $ 250,000,000 | $ 250,000,000 | $ 250,000,000 | $ 300,000,000 | $ 300,000,000 | $ 300,000,000 | $ 300,000,000 | $ 300,000,000 |  |  | $ 226,000,000 | $ 172,000,000 |  | $ 172,000,000 | $ 180,000,000 | $ 180,000,000 | $ 527,000,000 | $ 491,000,000 |  |  | $ 29,000,000 |  |  |  | $ 3,925,000,000 | [5] | $ 3,875,000,000 | [5] |  |  | $ 300,000,000 | [5] |  |  | $ 375,000,000 | [5] | $ 200,000,000 | [5] | $ 200,000,000 | [5] | $ 225,000,000 | [5] | $ 225,000,000 | [5] | $ 50,000,000 | [5] | $ 50,000,000 | [5] | $ 350,000,000 | [5] | $ 350,000,000 | [5] | $ 250,000,000 | [5] | $ 250,000,000 | [5] | $ 100,000,000 | [5] | $ 100,000,000 | [5] | $ 250,000,000 | [5] | $ 250,000,000 | [5] | $ 350,000,000 | [5] | $ 350,000,000 | [5] | $ 500,000,000 | [5] | $ 500,000,000 | [5] | $ 300,000,000 | [5] | $ 300,000,000 | [5] | $ 100,000,000 | [5] | $ 100,000,000 | [5] | $ 250,000,000 | [5] | $ 250,000,000 | [5] | $ 375,000,000 | [5] | $ 52,000,000 | [5] | $ 35,000,000 | [5] | $ 263,000,000 | [5] | $ 175,000,000 | [5] | $ 175,000,000 | [5] | $ 50,000,000 | [5] | $ 50,000,000 | [5] | $ 50,000,000 | [5] | $ 50,000,000 | [5] | $ 1,658,000,000 | $ 1,178,000,000 | $ 480,000,000 |  | $ 180,000,000 | [8] |  |  |
Interest-bearing Domestic Deposit, Brokered |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 527,000,000 |  | 462,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Principal amounts outstanding | 7,245,000,000 | 7,093,000,000 | 4,341,000,000 | 4,329,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Current portion of long-term debt | (519,000,000) | (1,033,000,000) | (41,000,000) | (339,000,000) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net unamortized discount | (16,000,000) | (20,000,000) | (3,000,000) | (3,000,000) | 13,000,000 | 17,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total long-term debt | 6,710,000,000 | 6,040,000,000 | 4,297,000,000 | 3,987,000,000 | 2,205,000,000 | 1,875,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Bear interest at three-month LIBOR plus a spread, in basis points |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | three-month LIBOR |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Three-month LIBOR plus a spread, in basis points |  |  |  |  |  |  | 2.50% | 2.00% |  |  |  |  |  |  |  | 0.95% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.00% | 2.50% |  |  |  |
Interest rate at period end |  |  |  |  |  |  | 2.71% |  |  |  |  |  |  |  |  |  | 1.35% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.71% |  |  |  |
Certificate of deposit face value |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ (1,000) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Weighted-average Interest Rate (%) |  |  |  |  |  |  |  |  | 5.72% |  | 5.65% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5.19% |  | 5.52% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
[1] | The weighted-average interest rate for Consumers’ Securitization bonds was 5.72 percent at December 31, 2012 and 5.65 percent at December 31, 2011.
[2] | CMS Energy’s contingently convertible notes. CMS Energy’s 2.875 percent senior notes were converted in January and April 2012. See the “Contingently Convertible Securities” section in this Note for further discussion of the conversion features.
[3] | In February 2012, CMS Energy retired the 7.75 percent Trust Preferred Securities.
[4] | The weighted-average interest rate for EnerBank’s certificates of deposit was 1.16 percent at December 31, 2012 and 1.33 percent at December 31, 2011. EnerBank’s primary deposit product consists of brokered certificates of deposit with varying maturities and having a face value of $1,000.
[5] | The weighted-average interest rate for Consumers’ FMBs was 5.19 percent at December 31, 2012 and 5.52 percent at December 31, 2011.
[6] | In May 2012, Consumers retired its 5.375 percent FMBs.
[7] | CMS Energy’s contingently convertible notes. See the “Contingently Convertible Securities” section in this Note for further discussion of the conversions.
[8] | Outstanding borrowings bear interest at an annual interest rate of LIBOR plus 2.50 percent (2.71 percent at December 31, 2012). CMS Energy used these proceeds to retire the 7.75 percent Trust Preferred Securities and floating-rate senior notes due January 2013. In February 2013, the term loan facility was amended, reducing the annual interest rate to LIBOR plus 2.00 percent.

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- Definition The percentage points added to the reference rate to compute the variable rate on the debt instrument. + References No definition available. + Details
Name: | us-gaap_DebtInstrumentBasisSpreadOnVariableRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
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- Definition Including current and noncurrent portions, aggregate carrying amount of long-term borrowings as of the balance sheet date before deducting unamortized discount or premiums (if any). May include notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, which had initial maturities beyond one year or beyond the normal operating cycle, if longer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 9 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number APB14-1 -Paragraph 31 -Subparagraph b -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20 -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 + Details
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- Definition The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR. + References No definition available. + Details
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- Definition The stated principal amount of the debt instrument at time of issuance, which may vary from the carrying amount because of unamortized premium or discount. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=6584090&loc=d3e28878-108400 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 21 -Paragraph 16, 20 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. + Details
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- Definition The effective interest rate at the end of the reporting period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Description of the maturity date of the debt instrument including whether the debt matures serially and, if so, a brief description of the serial maturities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(2)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 129 -Paragraph 2, 4 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. + Details
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- Definition The amount of debt discount (net of debt premium) that was originally recognized at the issuance of the instrument that has yet to be amortized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 21 -Paragraph 16 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28555-108399 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28567-108399 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=6584090&loc=d3e28878-108400 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28541-108399 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 21 -Paragraph 20 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. + Details
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- Definition This element represents the fair value of the face or notional amount of a contract right or obligation that meets the definition of an asset or liability reported in the financial statements of the entity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 3 -Subparagraph a -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Underlying -URI http://asc.fasb.org/extlink&oid=6527499 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 10 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6431724&loc=d3e32938-113948 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 20 -Section 10 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6438156&loc=d3e57880-113973 + Details
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- Definition Carrying amount of long-term debt, net of unamortized discount or premium, scheduled to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19,20) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20 -Article 5 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19 -Article 5 + Details
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