Vectren Fuels Pending Acquisition (Details) (Vectren Fuels [Member], Subsequent Event [Member], USD $) In Millions, unless otherwise specified	6 Months Ended	0 Months Ended
	Jun. 30, 2014 mi	Jul. 03, 2014 Scenario, Forecast [Member] site	Jul. 03, 2014 Scenario, Forecast [Member] Maximum [Member]
Business Acquisition [Line Items]
Date of acquisition agreement	Jul. 01, 2014
Number of mines purchased		3
Acquired mine, distance from previously owned mine	7
Business acquisition purchase price		$ 296	$ 325