Derivative Financial Instruments (Narrative) (Details) bbl in Millions		3 Months Ended			9 Months Ended		12 Months Ended
		Sep. 30, 2015 USD ($) bbl	Mar. 31, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) bbl	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($) bbl
Derivative [Line Items]
Debt Instrument, Face Amount		$ 3,400,000,000.0			$ 3,400,000,000.0		$ 2,900,000,000.0
Net payment on financial derivatives					(42,908,000)	$ (3,613,000)
Net loss on cash flow hedges(1)	[1]	(3,410,000)		$ (1,830,000)	(16,939,000)	$ (5,443,000)
Energy commodity derivatives deposits		49,447,000			49,447,000		84,463,000
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months					(1,500,000)
Tank bottoms and linefill		$ 36,491,000			$ 36,491,000		$ 42,585,000
Fair Value Hedging [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | bbl		0.7			0.7
Fair Value Hedging [Member] | NYMEX Commodity Contracts [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | bbl		0.7			0.7		0.7
Tank bottoms and linefill		$ (19,400,000)			$ (19,400,000)		$ (13,300,000)
Gain (Loss) from Components Excluded from Assessment of Fair Value Hedge Effectiveness, Net		(1,700,000)			4,600,000
Two Thousand Fifteen Interest Rate Swaps [Member] | Cash Flow Hedging [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative, Notional Amount		150,000,000			150,000,000
Derivative Asset, Fair Value, Gross Asset		600,000			600,000
Derivative Liability, Fair Value, Gross Liability		$ 1,100,000			$ 1,100,000
Two Thousand Fourteen Interest Rate Swaps [Member] | Cash Flow Hedging [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative, Notional Amount			$ 250,000,000
Debt Instrument, Face Amount			$ 250,000,000.0
Debt Instrument, Interest Rate, Stated Percentage			4.20%
Net payment on financial derivatives			$ (42,900,000)
Net loss on cash flow hedges(1)			$ (16,400,000)				$ (26,500,000)

[1] See Note 8–Derivative Financial Instruments for details of the amount of gain/loss recognized in accumulated other comprehensive loss ("AOCL") for derivative financial instruments and the amount of gain/loss reclassified from AOCL into income.