Disposals of Long-Lived Assets (Details Textual) (USD $)	12 Months Ended			1 Months Ended	0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Sep. 30, 2010	Jun. 02, 2014	Jun. 01, 2014
Cash proceeds from divestiture	$ 0	$ 0	$ 12,250,000
Corporate and other [Member]
Impairment of Leasehold	11,900,000
Crude [Member] | White Cliffs Pipeline, LLC [Member]
Gain (loss) on deconsolidation, pre-tax				(6,800,000)
Eastern Oklahoma gas gathering assets [Member] | SemGas [Member]
Proceeds from sale of property, plant and equipment					2,400,000
Disposal group, including discontinued operation, property, plant and equipment						22,500,000
Residential Division [Member] | SemStream [Member]
Disposal group, including discontinued operation, property, plant and equipment			9,400,000
Gain (loss) on disposal of discontinued operation, pre-tax			3,090,000
Cash proceeds from divestiture			12,300,000
Loss (gain) on impairment or disposal of long-lived assets, net [Member] | Crude [Member] | White Cliffs Pipeline, LLC [Member]
Gain (loss) on deconsolidation, pre-tax			3,500,000
Loss (gain) on impairment or disposal of long-lived assets, net [Member] | Eastern Oklahoma gas gathering assets [Member] | SemGas [Member]
Gain (loss) on disposal					(20,100,000)
Loss (gain) on impairment or disposal of long-lived assets, net [Member] | Residential Division [Member] | SemStream [Member]
Gain (loss) on disposal of discontinued operation, pre-tax			$ 3,090,000