Reconciliation of income and expenses (Details 8) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss from discontinued operations	[1]	$ (3,190)	$ (276,102)	$ (1,504)	$ (294,138)
Loss from discontinued operations attributable to noncontrolling interest		0	(120,651)	0	(131,691)
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		130	74,756	235	122,732
Operating expenses		1,205	443,756	(5,372)	513,526
Operating income (loss)		(1,075)	(369,000)	5,607	(390,794)
Other income (expense)		3	183	(13)	387
Interest expense		239	832	239	1,753
Income (loss) from discontinued operations before income taxes		(1,311)	(369,649)	5,355	(392,160)
Income taxes		1,879	(93,547)	6,859	(98,022)
Loss from discontinued operations		(3,190)	(276,102)	(1,504)	(294,138)
Loss from discontinued operations attributable to noncontrolling interest		0	(120,651)	0	(131,691)
Loss from discontinued operations attributable to the Company		(3,190)	(155,451)	(1,504)	(162,447)
Discontinued operations, held-for-sale or disposed of by sale [Member] | Refining [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Pretax income (loss) attributable to the Company		$ 0	$ (244,000)	$ 6,900	$ (253,900)

[1] Includes eliminations for the presentation of income tax adjustments between continuing and discontinued operations.