Regulatory Assets & Liabilities (Tables)

12 Months Ended

Dec. 31, 2017

Regulatory Assets and Liabilities Disclosure [Abstract]

Schedule of Regulatory Assets

Regulatory assets consist of the following:

	At December 31,
(In millions)	2017		2016
Future amounts recoverable from ratepayers related to:
Benefit obligations (See Note 9)	$	102.8	$	102.6
Net deferred income taxes (See Note 8)	6.2		(17.1		)
Asset retirement obligations & other	24.3		—
	133.3		85.5
Amounts deferred for future recovery related to:
Cost recovery riders & other	142.4		91.6
	142.4		91.6
Amounts currently recovered in customer rates related to:
Indiana authorized trackers	75.9		64.2
Ohio authorized trackers	28.4		22.2
Loss on reacquired debt & hedging costs	22.7		24.1
Deferred coal costs and other	14.1		21.2
	141.1		131.7
Total regulatory assets	$	416.8	$	308.8