Commitments and Contingencies, Environmental Contingencies - Unrecorded Unconditional Purchase Obligation (Details) - National Ambient Air Quality Standards for Ozone [Member]	Dec. 31, 2015 Period
Environmental Requirements [Abstract]
Number of hours measured for standard	8
Revised Level of Air Quality Concentrations (in parts per billion)	70
Former Level of Air Quality Concentrations (in parts per billion)	75