Derivative Instruments (Tables)

6 Months Ended

Jun. 30, 2013

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of commodity derivatives

	2013	2014	2015
Oil sales, Bbl/D	19,800	21,000	3,000
Natural gas purchases, MMBtu/D	10,000	—	—

Schedule of crude oil three way collars entered

Crude Oil Sales Three-Way Collars
Term	Index	Average Barrels Per Day	Sold Put / Purchased Put / Sold Call
Full year 2013 and 2014	ICE Brent	1,000	$80.00 / $100.00 / $114.05
Full year 2014	NYMEX WTI	1,000	$70.00 / $90.00 / $102.00

Schedule of Crude Oil NYMEX WTI Swaps Entered

Crude Oil Sales (NYMEX WTI) Swaps
Term	Average Barrels Per Day	Weighted Average Price
Full year 2014	11,500	$90.14

Schedule of derivative assets and liabilities

(in millions)		June 30, 2013
Description	Balance Sheet Classification	Gross Amounts of Recognized Assets or Liabilities		Gross Amounts Offset in the Condensed Balance Sheets			Net Amounts of Assets or Liabilities Presented in the Condensed Balance Sheets
Assets
Commodity derivative instruments	Current	$	23.8	$	(5.5	)	$	18.3
Commodity derivative instruments	Long-term	35.0		(0.1		)	34.9
Total assets		$	58.8	$	(5.6	)	$	53.2
Liabilities
Commodity derivative instruments	Current	$	5.4	$	(5.4	)	$	—
Commodity derivative instruments	Long-term	0.2		(0.2		)	—
Total liabilities		$	5.6	$	(5.6	)	$	—

(in millions)		December 31, 2012
Description	Balance Sheet Classification	Gross Amounts of Recognized Assets or Liabilities		Gross Amounts Offset in the Condensed Balance Sheets			Net Amounts of Assets or Liabilities Presented in the Condensed Balance Sheets
Assets
Commodity derivative instruments	Current	$	16.4	$	(1.7	)	$	14.7
Commodity derivative instruments	Long-term	10.9		—			10.9
Total assets		$	27.3	$	(1.7	)	$	25.6
Liabilities
Commodity derivative instruments	Current	$	2.8	$	(1.7	)	$	1.1
Commodity derivative instruments	Long-term	1.2		—			1.2
Total liabilities		$	4.0	$	(1.7	)	$	2.3

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

		Three Months Ended						Six Months Ended
(in millions)	Location of Loss (Gain) Recognized in Earnings	June 30,						June 30,
Description of Loss (Gain)		2013			2012			2013			2012
Commodity
Loss reclassified from AOCL into earnings (amortization of frozen amounts)	Oil and natural gas sales	$	—		$	2.5		$	—		$	5.2
Gain recognized in earnings (cash settlements and mark-to-market movements)	Realized and unrealized gain on derivatives, net	(35.6		)	(113.1		)	(34.9		)	(84.6		)
Interest rate
Gain reclassified from AOCL into earnings (amortization of frozen amounts)	Interest	$	—		$	(0.9	)	$	—		$	(1.5	)

Schedule of Crude Oil NYMEX WTI to ICE Brent Basis Swaps Entered

Crude Oil Sales (NYMEX WTI to ICE Brent) Basis Swaps
Term	Average Barrels Per Day	Weighted Average Price
Full year 2014	10,000	$11.60
Full year 2015	8,000	$11.60

Schedule of Crude Oil NYMEX WTI to Midland Basis Swaps Entered

Crude Oil Sales (NYMEX WTI to Midland) Basis Swaps
Term	Average Barrels Per Day	Weighted Average Price
April 2013 - December 2013	4,000	$1.48