Regulatory Matters (Tables)

12 Months Ended

Dec. 31, 2013

Regulatory Assets and Liabilities Disclosure [Abstract]

Regulatory Assets

At December 31, (in millions)	2013			2012
Assets
Reacquisition premium on debt	$	6.5		$	8.6
R. M. Schahfer Unit 17 and Unit 18 carrying charges and deferred depreciation (see Note 1-H)	2.3			5.5
Unrecognized pension benefit and other postretirement benefit costs (see Note 12)	842.2			1,345.7
Other postretirement costs	67.7			66.3
Environmental costs (see Note 20-D)	68.7			77.5
Regulatory effects of accounting for income taxes (see Note 1-V)	266.8			245.7
Underrecovered gas and fuel costs (see Note 1-P and 1-Q)	46.4			45.0
Depreciation (see Note 1-H)	113.6			113.9
Uncollectible accounts receivable deferred for future recovery	10.5			6.1
Asset retirement obligations (see Note 7)	10.5			16.1
Losses on derivatives (see Note 9)	2.0			17.1
Post-in-service carrying charges	73.1			61.2
EERM operation and maintenance and depreciation deferral	5.9			9.8
MISO (see Note 8)	19.2			28.8
Sugar Creek carrying charges and deferred depreciation (see Note 1-H)	56.8			71.2
Other	119.2			113.7
Total Assets	$	1,711.4		$	2,232.2
Less amounts included as Underrecovered gas and fuel cost	(46.4		)	(45.0		)
Total Regulatory Assets reflected in Current Regulatory Assets and Other Regulatory Assets	$	1,665.0		$	2,187.2

Regulatory Liabilities

At December 31, (in millions)	2013			2012
Liabilities
Overrecovered gas and fuel costs (see Notes 1-P and 1-Q)	$	32.2		$	22.1
Cost of removal (see Note 7)	1,435.2			1,437.5
Regulatory effects of accounting for income taxes (see Note 1-V)	60.4			76.9
Unrecognized pension benefit and other postretirement benefit costs (see Note 12)	49.4			0.4
Other postretirement costs	111.9			97.4
Percentage of income plan	—			16.0
Off-system sales margin sharing	3.7			5.8
Other	69.4			130.9
Total Liabilities	$	1,762.2		$	1,787.0
Less amounts included as Overrecovered gas and fuel cost	(32.2		)	(22.1		)
Total Regulatory Liabilities reflected in Current Regulatory Liabilities and Other Regulatory Liabilities and Other Removal Costs	$	1,730.0		$	1,764.9