Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2013

Fair Value Disclosures [Abstract]

Fair value of financial assets and liabilities

The fair value of financial assets and liabilities at March 31, 2013, is shown in the table below:

	Fair Value Measurements
	March 31, 2013
	Gross Amounts of Assets and Liabilities						Netting Adjustments(1)			Net Amounts Presented on the Condensed Consolidated Balance Sheet
	Level 1		Level 2		Level 3
	(in millions)
Financial Assets
Commodity derivative instruments - short-term	$	—	$	93.7	$	—	$	(8.1	)	$	85.6
Commodity derivative instruments - long-term	—		2.7		—		(0.2		)	2.5
Total financial assets	$	—	$	96.4	$	—	$	(8.3	)	$	88.1
Financial Liabilities
Commodity derivative instruments - short-term	$	—	$	21.1	$	—	$	(8.1	)	$	13.0
Interest rate swaps - short-term	—		2.5		—		—			2.5
Commodity derivative instruments - long-term	—		0.2		—		(0.2		)	—
Interest rate swaps - long-term	—		3.2		—		—			3.2
Total financial liabilities	$	—	$	27.0	$	—	$	(8.3	)	$	18.7

The fair value of financial assets and liabilities at December 31, 2012, is shown in the table below:

	Fair Value Measurements
	December 31, 2012
	Gross Amounts of Assets and Liabilities						Netting Adjustments(1)			Net Amounts Presented on the Condensed Consolidated Balance Sheet
	Level 1		Level 2		Level 3
	(in millions)
Financial Assets
Commodity derivative instruments - short-term	$	—	$	189.7	$	—	$	(1.0	)	$	188.7
Commodity derivative instruments - long-term	—		4.2		—		(0.1		)	4.1
Total financial assets	$	—	$	193.9	$	—	$	(1.1	)	$	192.8
Financial Liabilities
Commodity derivative instruments - short-term	$	—	$	1.0	$	—	$	(1.0	)	$	—
Interest rate swaps - short-term	—		2.6		—		—			2.6
Commodity derivative instruments - long-term	—		0.1		—		(0.1		)	—
Interest rate swaps - long-term	—		3.6		—		—			3.6
Total financial liabilities	$	—	$	7.3	$	—	$	(1.1	)	$	6.2

Fair value and related carrying amount of certain financial instruments

The following table discloses the fair value and related carrying amount of certain financial instruments not disclosed in other notes to the condensed consolidated financial statements in this quarterly report on Form 10-Q:

	Carrying Amount		Level 1 Fair Value		Carrying Amount		Level 1 Fair Value
	March 31, 2013				December 31, 2012
	(in millions)
Financial liabilities
Checks outstanding in excess of cash balances	$	99.7	$	99.7	$	39.7	$	39.7
Long-term debt	$	3,367.5	$	3,535.7	$	3,206.9	$	3,420.7