Commitments and Contingencies, Environmental Contingencies (Details) $ in Millions	1 Months Ended	3 Months Ended
	Feb. 29, 2016	Mar. 31, 2016 USD ($)
Regional Haze Rules
Environmental Requirements [Abstract]
Amount spent on installation of emission controls		$ 75.2
Implementation of the National Ambient Air Quality Standard for Sulfur Dioxide
Environmental Requirements [Abstract]
Number of phases under a consent decree which the EPA is requiring states to evaluate areas for attainment		3
Number of years unclassifiable areas will be monitored	3 years
Number of months in which the state would have to submit an implementation plan for the respective nonattainment areas		18 months
Number of years for the state to achieve the designated attainment standard		5 years