Capitalized Exploratory Well Costs (Tables)

12 Months Ended

Dec. 31, 2014

Capitalized Exploratory Well Costs [Abstract]

Capitalized Exploratory Well Costs, Roll Forward [Table Text Block]

	2014			2013			2012
	(in millions)
Balance at January 1,	$	2.6		$	2.1		$	5.0
Additions to capitalized exploratory well costs pending the determination of proved reserves	13.7			2.7			12.7
Reclassifications to proved properties after the determination of proved reserves	—			(2.2		)	(15.6		)
Capitalized exploratory well costs charged to expense	(3.7		)	—			—
Balance at December 31,	$	12.6		$	2.6		$	2.1