Regulatory Assets and Liabilities (Tables)

12 Months Ended

Dec. 31, 2012

Regulatory Assets and Liabilities (Tables) [Abstract]

Regulatory assets and liabilities

Our regulatory assets and liabilities as of December 31 consist of:

	2012		2011
	(Millions of Dollars)
Regulatory Assets
Deferred unrecognized pension costs	$	731.5	$	647.8
Deferred income tax related	176.5		121.2
Escrowed electric transmission costs	114.1		118.3
Escrowed conservation	73.5		31.5
Deferred unrecognized OPEB costs	61.6		102.9
Deferred plant related -- capital lease	66.6		73.2
Deferred environmental costs	47.4		48.5
Other, net	109.1		122.3
Total regulatory assets	$	1,380.3	$	1,265.7
Regulatory Liabilities
Deferred cost of removal obligations	$	725.0	$	728.2
Escrowed bad debt costs	81.1		69.0
Other, net	62.2		118.7
Total regulatory liabilities	$	868.3	$	915.9