Investment in Sunrise Energy (Condensed Balance Sheet - Sunrise) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Current assets	$ 81,987	$ 84,409
Total assets	575,628	579,585
Total liabilities	372,856	389,710
Total liabilities and stockholders' equity	575,628	$ 579,585
Sunrise Energy [Member]
Current assets	2,300
Oil and gas properties, net	8,105
Total assets	10,405
Total liabilities	769
Members' capital	9,636
Total liabilities and stockholders' equity	$ 10,405