JOINTLY OWNED UTILITY PLANT/COORDINATED SERVICES Additional Information (Details) $ in Millions	Dec. 31, 2015 USD ($)
Municipal Power Agency | Lines
Jointly Owned Utility Plant Interests
Ownership percentage	50.40%
ITCTransmission | Lines
Jointly Owned Utility Plant Interests
Net investment including assets under construction	$ 28.8
METC | Substations
Jointly Owned Utility Plant Interests
Net investment including assets under construction	13.9
Assets under construction	$ 0.1
METC | Substations | Minimum
Jointly Owned Utility Plant Interests
Ownership percentage	6.30%
METC | Substations | Maximum
Jointly Owned Utility Plant Interests
Ownership percentage	92.00%
METC | Lines
Jointly Owned Utility Plant Interests
Net investment including assets under construction	$ 41.0
METC | Lines | Minimum
Jointly Owned Utility Plant Interests
Ownership percentage	1.00%
METC | Lines | Maximum
Jointly Owned Utility Plant Interests
Ownership percentage	41.90%
ITC Midwest | Substations
Jointly Owned Utility Plant Interests
Net investment including assets under construction	$ 18.4
Assets under construction	$ 0.7
ITC Midwest | Substations | Minimum
Jointly Owned Utility Plant Interests
Ownership percentage	28.00%
ITC Midwest | Substations | Maximum
Jointly Owned Utility Plant Interests
Ownership percentage	80.00%
ITC Midwest | Lines
Jointly Owned Utility Plant Interests
Net investment including assets under construction	$ 32.9
Assets under construction	$ 0.1
ITC Midwest | Lines | Minimum
Jointly Owned Utility Plant Interests
Ownership percentage	48.00%
ITC Midwest | Lines | Maximum
Jointly Owned Utility Plant Interests
Ownership percentage	80.00%
Electric Cooperative | Lines
Jointly Owned Utility Plant Interests
Ownership percentage	49.00%
ITC Great Plains | Lines
Jointly Owned Utility Plant Interests
Ownership percentage	51.00%
Net investment including assets under construction	$ 6.5