Regulatory Matters (Tables)

12 Months Ended

Dec. 31, 2014

Regulatory Assets and Liabilities Disclosure [Abstract]

Regulatory Assets

At December 31, (in millions)	2014			2013
Assets
Unrecognized pension benefit and other postretirement benefit costs (see Note 10)	$	1,031.2		$	842.2
Other postretirement costs	57.7			67.7
Environmental costs (see Note 18-D)	65.9			68.7
Regulatory effects of accounting for income taxes (see Note 1-V)	239.7			266.8
Underrecovered gas and fuel costs (see Note 1-P and 1-Q)	32.0			46.4
Depreciation (see Note 1-H)	116.4			113.6
Uncollectible accounts receivable deferred for future recovery	26.1			10.5
Post-in-service carrying charges	87.8			73.1
EERM operation and maintenance and depreciation deferral	31.1			5.9
Sugar Creek carrying charges and deferred depreciation (see Note 1-H)	42.5			56.8
DSM Program	37.9			27.8
Other	153.6			131.9
Total Assets	$	1,921.9		$	1,711.4
Less amounts included as Underrecovered gas and fuel cost	(32.0		)	(46.4		)
Total Regulatory Assets reflected in Current Regulatory Assets and Other Regulatory Assets	$	1,889.9		$	1,665.0

Regulatory Liabilities

At December 31, (in millions)	2014			2013
Liabilities
Overrecovered gas and fuel costs (see Notes 1-P and 1-Q)	$	45.6		$	32.2
Cost of removal (see Note 6)	1,445.9			1,435.2
Regulatory effects of accounting for income taxes (see Note 1-V)	53.2			60.4
Unrecognized pension benefit and other postretirement benefit costs (see Note 10)	18.4			49.4
Other postretirement costs	149.3			111.9
Other	69.4			73.1
Total Liabilities	$	1,781.8		$	1,762.2
Less amounts included as Overrecovered gas and fuel cost	(45.6		)	(32.2		)
Total Regulatory Liabilities reflected in Current Regulatory Liabilities and Other Regulatory Liabilities and Other Removal Costs	$	1,736.2		$	1,730.0