Summary Of Significant Accounting Policies (Significant Unobservable Inputs in Asset Valuation) (Details)	Dec. 31, 2015
Vermont Yankee [Member]
Weighted average cost of capital, Weighted Average	7.50%
Long-term pre-tax operating margin (cash basis), Weighted Average	7.00%
Pilgrim [Member]
Weighted average cost of capital, Weighted Average	7.90%
Long-term pre-tax operating margin (cash basis), Weighted Average	8.10%
Pilgrim [Member] | Minimum [Member]
Weighted average cost of capital, Range	7.50%
Long-term pre-tax operating margin (cash basis), Range	2.40%
Pilgrim [Member] | Maximum [Member]
Weighted average cost of capital, Range	8.00%
Long-term pre-tax operating margin (cash basis), Range	10.60%
FitzPatrick [Member]
Weighted average cost of capital, Weighted Average	7.50%
Long-term pre-tax operating margin (cash basis), Weighted Average	10.20%
Palisades [Member]
Weighted average cost of capital, Weighted Average	7.50%
Long-term pre-tax operating margin (cash basis), Weighted Average	30.80%