Equity Investment in Sunrise Energy (Condensed Balance Sheet - Sunrise) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets	$ 66,615	$ 84,409
Total assets	545,490	579,585
Total liabilities	338,670	389,710
Total liabilities and stockholders' equity	545,490	579,585
Sunrise Energy [Member]
Current assets	2,217	3,580
Oil and gas properties, net	7,981	7,130
Total assets	10,198	10,710
Total liabilities	716	1,080
Members' capital	9,482	9,630
Total liabilities and stockholders' equity	$ 10,198	$ 10,710