Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2016

Fair Value Disclosures [Abstract]

Schedule of assets and liabilities measured at estimated fair value on a recurring basis

The following table presents information about our gross assets and liabilities that are measured at fair value on a recurring basis as of December 31, 2016 and 2015 (in millions):

	Fair Value Measurements as of December 31, 2016
		Level 1 Inputs		Level 2 Inputs		Level 3 Inputs		Total Fair Value
Assets:
Commodities contracts	$	273.6	$	55.3	$	2.3	$	331.2
Foreign currency contracts		—		16.0		—		16.0
Cash surrender value of life insurance		—		4.0		—		4.0
Total assets at fair value	$	273.6	$	75.3	$	2.3	$	351.2
Liabilities:
Commodities contracts	$	236.6	$	88.8	$	0.7	$	326.1
Foreign currency contracts		—		6.4		—		6.4
Total liabilities at fair value	$	236.6	$	95.2	$	0.7	$	332.5

	Fair Value Measurements as of December 31, 2015
		Level 1 Inputs		Level 2 Inputs		Level 3 Inputs		Total Fair Value
Assets:
Commodities contracts	$	262.0	$	252.0	$	3.3	$	517.3
Foreign currency contracts		—		12.4		—		12.4
Cash surrender value of life insurance		—		2.4		—		2.4
Total assets at fair value	$	262.0	$	266.8	$	3.3	$	532.1
Liabilities:
Commodities contracts	$	339.8	$	123.4	$	0.2	$	463.4
Foreign currency contracts		—		5.0		—		5.0
Total liabilities at fair value	$	339.8	$	128.4	$	0.2	$	468.5

Schedule of derivative instruments at fair value and their locations on the balance sheets

The following tables summarize those commodity derivative balances subject to the right of setoff as presented on our consolidated balance sheet. We have elected to offset the recognized fair value amounts for multiple derivative instruments executed with the same counterparty in our financial statements when a legal right offset exists.

	Fair Value as of December 31, 2016
		Gross Amounts Recognized		Gross Amounts Offset		Net Amounts Presented		Cash Collateral		Gross Amounts Without Right of Offset		Net Amounts
Assets:
Commodities contracts	$	331.2	$	249.7	$	81.5	$	27.1	$	—	$	54.5
Foreign currency contracts		16.0		5.1		10.9		—		—		10.9
Total assets at fair value	$	347.2	$	254.8	$	92.4	$	27.1	$	—	$	65.3
Liabilities:
Commodities contracts	$	326.1	$	249.7	$	76.5	$	2.0	$	—	$	74.5
Foreign currency contracts		6.4		5.1		1.2		—		—		1.2
Total liabilities at fair value	$	332.5	$	254.8	$	77.7	$	2.0	$	—	$	75.7

	Fair Value as of December 31, 2015
		Gross Amounts Recognized		Gross Amounts Offset		Net Amounts Presented		Cash Collateral		Gross Amounts Without Right of Offset		Net Amounts
Assets:
Commodities contracts	$	517.3	$	257.2	$	260.1	$	28.4	$	—	$	231.7
Foreign currency contracts		12.4		4.1		8.2		—		—		8.2
Total assets at fair value	$	529.6	$	261.3	$	268.4	$	28.4	$	—	$	240.0
Liabilities:
Commodities contracts	$	463.4	$	257.2	$	206.3	$	140.8	$	—	$	65.5
Foreign currency contracts		5.0		4.1		0.9		—		—		0.9
Total liabilities at fair value	$	468.5	$	261.3	$	207.2	$	140.8	$	—	$	66.4

Schedule of assets and liabilities that are measured at fair value on a recurring basis that utilized Level 3 inputs

The following table presents a reconciliation of beginning and ending balances of assets and liabilities that are measured at fair value on a recurring basis that utilized significant Level 3 inputs for the periods presented (in millions):

	2016			2015
Fair value at beginning of the period	$	3.0		$	2.8
Included in earnings	(1.3		)	4.2
Settlements	—			4.8
Transfers in	—			0.9
Transfers out	0.1			—
Fair value at end of period	$	1.6		$	3.0
Gains for the period included in earnings attributable to the change in unrealized gains relating to derivatives still held at the reporting date	$	1.6		$	2.6