Assets Held-for-Sale and Discontinued Operations (Details 2) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Income (loss) from discontinued operations
Income (loss) from discontinued operations, net of tax	$ (45,275)	$ 4,005	$ (41,067)	$ 4,488
Assets Held-for-sale
Income (loss) from discontinued operations
Impairment charge	51,000
Impairment of note receivable	4,000
Gas transport and processing
Contracts for gas transport and processing
Contractual Obligation	35,300		35,300
Gas transport and processing | Disposal Group, Held-for-sale, Not Discontinued Operations
Contracts for gas transport and processing
Recorded contratucal commitments			20,300		$ 40,200
Gas transport and processing | Disposal Group, Held-for-sale, Not Discontinued Operations | Accrued liabilities
Contracts for gas transport and processing
Recorded contratucal commitments			5,900		$ 19,600
Oil and Gas | Discontinued Operations, Held-for-sale or Disposed of by Sale
Income (loss) from discontinued operations
Operating revenues	432	2,314	2,737	10,842
Income (loss) from discontinued operations	(1,388)	(509)	(3,903)	1,027
Less: Impairment charges or other (gains) and losses on sale of wholly owned assets and obligations	55,044	(7,312)	56,075	(5,901)
Less: Income tax expense (benefit)	(11,157)	2,798	(18,911)	2,440
Income (loss) from discontinued operations, net of tax	$ (45,275)	$ 4,005	$ (41,067)	$ 4,488