Investments in unconsolidated companies - Summarized financial data for investments in unconsolidated companies (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Summarized financial data for OEH's unconsolidated companies
Current assets	$ 44,438		$ 44,438		$ 52,289
Property, plant and equipment, net	198,853		198,853		340,546
Other assets	33,312		33,312		37,917
Non-current assets	232,165		232,165		378,463
Total assets	276,603		276,603		430,752
Current liabilities, including $30,379 and $96,824 current portion of third-party debt	89,050		89,050		157,273
Long-term debt	18,855		18,855		27,014
Other liabilities	39,591		39,591		125,210
Non-current liabilities	58,446		58,446		152,224
Total shareholders’ equity	129,107		129,107		121,255
Total liabilities and shareholders’ equity	276,603		276,603		$ 430,752
Revenue	43,255	$ 45,626	77,091	$ 80,341
Gross profit	29,198	28,052	48,044	46,533
Net earnings	$ 2,526	$ 2,948	$ 3,322	$ 2,596