Vectren Fuels Acquisition (Narrative) (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
	Aug. 29, 2014	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Revenues		$ 64,853	$ 82,013	$ 95,253	$ 98,001	$ 100,622	$ 66,322	$ 38,460	$ 35,767	$ 340,120	$ 241,171	$ 153,870
Income before income taxes										$ 27,570	10,701	$ 29,598
Business acquisition purchase price											$ 311,453
Vectren Fuels [Member]
Business Acquisition [Line Items]
Business acquisition purchase price	$ 311,000