Investment in Sunrise Energy (Condensed Balance Sheet - Sunrise) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Current assets	$ 77,042	$ 84,409
Total assets	563,398	579,585
Total liabilities	356,051	389,710
Total liabilities and stockholders' equity	563,398	$ 579,585
Sunrise Energy [Member]
Current assets	2,325
Oil and gas properties, net	8,131
Total assets	10,456
Total liabilities	777
Members' capital	9,679
Total liabilities and stockholders' equity	$ 10,456