Related Parties (Tables)

12 Months Ended

Dec. 31, 2011

Related Parties (Tables) [Abstract]

Provided and received services from the associated companies

We provided and received services from the following associated companies during 2011, 2010 and 2009:

Equity Investee	2011		2010		2009
	(Millions of Dollars)
Services Provided
–ATC	$	10.8	$	16.9	$	22.3
Services Received
–ATC	$	219.2	$	220.8	$	196.0

Receivable and payable balances with ATC

As of December 31, 2011 and 2010, our Consolidated Balance Sheets included receivable and payable balances with ATC as follows:

Equity Investee	2011		2010
	(Millions of Dollars)
Services Provided
–ATC	$	0.7	$	0.9
Services Received
–ATC	$	18.1	$	18.5