Reconciliation of income and expenses (Details 3) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss from discontinued operations	$ (835)	$ (324,605)
Discontinued operations, held-for-sale or disposed of by sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating revenues	2,910	54,936
Operating expenses	4,470	572,952
Operating loss	(1,560)	(518,016)
Other income	6	1,881
Interest expense	13	21
Loss from discontinued operations before income taxes	(1,567)	(516,156)
Income taxes	(732)	(191,551)
Loss from discontinued operations	$ (835)	$ (324,605)