RETIREMENT BENEFITS AND ASSETS HELD IN TRUST Additional Information (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended		3 Months Ended	1 Months Ended	3 Months Ended			9 Months Ended
	Jun. 30, 2013 Retirement Plan Benefits	Jun. 30, 2013 Supplemental Retirement Benefit Plans	Dec. 31, 2013 Supplemental Retirement Benefit Plans Expectation	Sep. 30, 2013 Other Postretirement Benefit Plan	Dec. 31, 2013 Other Postretirement Benefit Plan Expectation	Sep. 30, 2013 Defined Contribution Plan	Sep. 30, 2012 Defined Contribution Plan	Sep. 30, 2013 Defined Contribution Plan	Sep. 30, 2012 Defined Contribution Plan
Retirement Benefits Disclosure
Employer contribution	$ 6.9	$ 0.6		$ 1.0
Additional current year contribution			0		1.5
Employer match contribution						$ 0.7	$ 0.7	$ 3.1	$ 2.4