REGULATORY ASSETS AND LIABILITIES Additional Information (Details) - USD ($) $ in Thousands		12 Months Ended
	Jan. 01, 2007	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jan. 31, 2007	Feb. 28, 2003
Regulatory Assets
Regulatory assets		$ 248,112	$ 229,105
Michigan
Regulatory Assets
State income tax rate		6.00%
ITCTransmission | ADIT Deferral
Regulatory Assets
Amortization of Acquisition Costs			3,000	$ 3,000
Regulatory assets						$ 60,600
Regulatory asset, amortization period		20 years
Amortization of regulatory asset		$ 3,000
ITCTransmission | Income Taxes Recoverable Related to Implementation of the Michigan Corporate Income Tax
Regulatory Assets
Regulatory asset, amortization period		23 years
METC | ADIT Deferral
Regulatory Assets
Amortization of Acquisition Costs			2,400	2,400
Regulatory assets					$ 42,500
Regulatory asset, amortization period	18 years
Amortization of regulatory asset		$ 2,400
METC | Regulatory Deferrals
Regulatory Assets
Amortization of Acquisition Costs			$ 800	$ 800
Regulatory assets					$ 15,400
Regulatory asset, amortization period		20 years
Amortization of regulatory asset		$ 800
METC | Income Taxes Recoverable Related to Implementation of the Michigan Corporate Income Tax
Regulatory Assets
Regulatory asset, amortization period		32 years