Related Parties (Tables)

12 Months Ended

Dec. 31, 2012

Related Parties (Tables) [Abstract]

Provided and received services from the associated companies

We provided and received services from the following associated companies during 2012, 2011 and 2010:

Equity Investee	2012		2011		2010
	(Millions of Dollars)
Services Provided
–ATC	$	8.2	$	10.8	$	16.9
Services Received
–ATC	$	222.7	$	219.2	$	220.8

Receivable and payable balances with ATC

As of December 31, 2012 and 2011, our Consolidated Balance Sheets included receivable and payable balances with ATC as follows:

Equity Investee	2012		2011
	(Millions of Dollars)
Services Provided
–ATC	$	0.5	$	0.7
Services Received
–ATC	$	18.6	$	18.1