Capitalized Exploratory Well Costs

12 Months Ended

Dec. 31, 2012

Capitalized Exploratory Well Costs [Abstract]

Suspended Well Costs Disclosure [Text Block]

Net changes in capitalized exploratory well costs are presented in the table below and exclude amounts that were capitalized and subsequently expensed in the period. The balance at December 31, 2012, 2011 and 2010, represents the amount of capitalized exploratory well costs that are pending the determination of proved reserves.

	2012			2011			2010
	(in millions)
Balance at January 1,	$	5.0		$	13.6		$	51.7
Additions to capitalized exploratory well costs pending the determination of proved reserves	12.7			—			12.2
Reclassifications to proved properties after the determination of proved reserves	(15.6		)	(8.3		)	(50.3		)
Capitalized exploratory well costs charged to expense	—			(0.3		)	—
Balance at December 31,	$	2.1		$	5.0		$	13.6