Derivative Contracts, Contracts Expiring in Next Twleve Months, Percent

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- Definition

The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4H
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624258-113959

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- Definition

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
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-Subparagraph (c)
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-Publisher FASB
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-Section 45
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-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
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- Definition

Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
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-Paragraph 4C
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4H
-Subparagraph (c)
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- Definition

Period remaining until the derivative contract matures, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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- Definition

The amount of cash or securities placed with a broker or counterparty as security for a trading or derivatives securities position which was partially obtained with funds provided by the broker dealer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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Risk Management (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivative [Line Items]
Collateral posted for commodity derivative instruments	$ 2.0		$ 4.3	$ 16.8
Products and services sold
Derivative [Line Items]
Gain (Loss) on derivative instruments not designated as hedging			7.8	18.9	$ 51.2
Commodity contract
Derivative [Line Items]
Gain (Loss) on derivative instruments not designated as hedging	5.4	$ 1.2
Aggregate fair value of commodity derivative instruments			$ 13.9	3.3
Collateral posted for commodity derivative instruments	$ 0.1			0.1
Price Risk Contracts \| Maximum
Derivative [Line Items]
Remaining maturity	36 months		28 months
Percent of contracts expiring in next twelve months	81.00%		81.00%
Commodity contract with credit contingent features
Derivative [Line Items]
Aggregate fair value of commodity derivative instruments	$ 4.8		$ 13.9
NYMEX Derivative Liability
Derivative [Line Items]
Aggregate fair value of commodity derivative instruments			14.3	20.8
Derivative Asset	4.6		14.3
NYMEX Margin Deposit
Derivative [Line Items]
NYMEX margin deposit	$ 0.9		$ 4.2	$ 26.7