Discontinued operations and divestitures (Operating Results) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total costs and expenses and other, net, excluding depreciation and amortization	$ 231,302	$ 385,363	$ 511,943	$ 845,628
Depreciation and amortization	22,685	14,212	45,402	27,820
Other operating loss	(167)	99	(177)	54
Income (loss) from discontinued operations, net of income taxes	0	(1,292)	1,215	(1,881)
Floating Storage Assets
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total revenues from third parties	0	15,683	791	33,175
Total costs and expenses and other, net, excluding depreciation and amortization	0	16,592	1,038	34,290
Depreciation and amortization	0	383	0	766
Other operating loss	0	0	1,462	0
Income (loss) from discontinued operations before income taxes	0	(1,292)	1,215	(1,881)
Income tax expense	0	0	0	0
Income (loss) from discontinued operations, net of income taxes	$ 0	$ (1,292)	$ 1,215	$ (1,881)