Assets Held-for-Sale and Discontinued Operations Disc Ops (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Income (loss) from discontinued operations
Income (loss) from Oil and Gas discontinued operations, net of tax	$ (439)	$ (926)
Gas transport and processing
Contracts for gas transport and processing
Contractual Obligation	15,700		$ 17,200
Gas transport and processing | Disposal Group, Held-for-sale, Not Discontinued Operations
Contracts for gas transport and processing
Recorded contractual commitments	11,600		12,500
Gas transport and processing | Disposal Group, Held-for-sale, Not Discontinued Operations | Accrued liabilities
Contracts for gas transport and processing
Recorded contractual commitments	5,600		$ 5,500
Oil and Gas | Discontinued Operations, Held-for-sale or Disposed of by Sale
Income (loss) from discontinued operations
Operating revenues	2,034	377
Income (loss) from discontinued operations	(590)	(1,326)
Less: Impairment charges or other (gains) and losses on sale of wholly owned assets (2)	20
Less: Income tax expense (benefit)	(171)	(400)
Income (loss) from Oil and Gas discontinued operations, net of tax	$ (439)	$ (926)