Regulatory Matters - MISO Return on Equity Complaints (Details) - FERC [Member]	Mar. 31, 2016
Return on Equity Complaint 1 [Member]
Loss Contingencies [Line Items]
Proposed Return on Common Equity	9.15%
Return on Equity Complaint 2 [Member]
Loss Contingencies [Line Items]
Proposed Return on Common Equity	8.67%
Return on Equity Complaints [Member]
Loss Contingencies [Line Items]
Proposed Return on Common Equity	10.32%