Equity Investment in Savoy (Condensed Balance Sheet - Savoy) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets	$ 66,615	$ 84,409
Other	16,528	18,849
Total assets	545,490	579,585
Total liabilities	338,670	389,710
Total liabilities and stockholders' equity	545,490	579,585
Savoy [Member]
Current assets	11,795	14,863
Oil and gas properties, net	21,659	27,549
Other	1,015	852
Total assets	34,469	43,264
Total liabilities	4,909	10,079
Partners' capital	29,560	33,185
Total liabilities and stockholders' equity	$ 34,469	$ 43,264