Derivative Instruments (Tables)

12 Months Ended

Dec. 31, 2011

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of commodity derivatives

	2012	2013	2014
Oil Bbl/D:	21,000	15,000	2,000
Natural Gas MMBtu/D:	15,000	—	—

Schedule of derivative assets and liabilities

	December 31, 2011
	Derivative Assets			Derivative Liabilities
(in millions)	Balance Sheet Classification	Fair Value		Balance Sheet Classification	Fair Value
Current:
Commodity	Derivative assets	$	6.1	Derivative liabilities	$	20.4
Long-term:
Commodity	Derivative assets	7.0		Derivative liabilities	15.5
Total derivatives		$	13.1		$	35.9

	December 31, 2010
	Derivative Assets			Derivative Liabilities
(in millions)	Balance Sheet Classification	Fair Value		Balance Sheet Classification	Fair Value
Current:
Commodity	Derivative assets	$	2.7	Derivative liabilities	$	84.9
Long-term:
Commodity	Derivative assets	2.1		Derivative liabilities	33.5
Total derivatives		$	4.8		$	118.4

Summary of (gains) losses before income taxes of derivative instruments recognized in the condensed statements of income (loss)

(in millions)		Year Ended December 31,
Derivatives cash flow hedging relationships	Location of (Gain) Loss Recognized in Earnings	2011	2010	2009
Commodity
Loss recognized in AOCL (effective portion)	Accumulated other comprehensive loss	—	—	206.4
(Gain) reclassified from AOCL into earnings (effective portion)	Sales of oil and natural gas	—	—	(58.8	)
(Gain) reclassified from AOCL into earnings (effective portion)	Earnings from discontinued operations	—	—	(20.5	)
Loss recognized in earnings (ineffective portion)	Realized and unrealized (gain) loss on derivatives, net	—	—	0.6
Loss reclassified from AOCL into earnings (amortization of frozen amounts)	Sales of oil and natural gas	60.9	18.4	—
Interest rate
Loss recognized in AOCL (effective portion)	Accumulated other comprehensive loss	—	—	2.7
Loss reclassified from AOCL into earnings (effective portion)	Interest	—	—	7.0
Loss reclassified from AOCL into earnings (amortization of frozen amounts)	Interest	0.8	8.3	—

(in millions)		Year Ended December 31,
Derivatives not designated as hedging instruments under authoritative guidance	Location of (Gain) Loss Recognized in Earnings	2011		2010	2009
Commodity
(Gain) loss recognized in earnings (cash settlements and mark-to-market movements)	Realized and unrealized (gain) loss on derivatives, net	(13.9	)	23.2	7.2
(Gain) loss recognized in earnings (cash settlements and mark-to-market movements)	Earnings from discontinued operations	—		—	0.5
Interest rate
(Gain) loss reclassified from AOCL into earnings (amortization of frozen amounts)	Realized and unrealized (gain) loss on derivatives, net	—		8.6	—