Investment in Sunrise Energy (Condensed Balance Sheet - Sunrise) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Current assets	$ 62,274	$ 66,615
Total assets	547,587	540,378
Total liabilities	335,141	333,558
Total liabilities and stockholders' equity	547,587	$ 540,378
Sunrise Energy [Member]
Current assets	2,204
Oil and gas properties, net	7,844
Total assets	10,048
Total liabilities	716
Members' capital	9,332
Total liabilities and stockholders' equity	$ 10,048