Commitments and Contingencies, Capital Commitments (Details) - Capital Commitments	12 Months Ended
	Dec. 31, 2016 MW kV
Upper Midwest Wind Projects
Capital Commitments [Abstract]
Public Utilities, Requested Total Wind Generation in MW	1,500
Public Utilities, Requested Self-Build Wind Generation in MW	750
Rush Creek Wind Farm
Capital Commitments [Abstract]
Public Utilities, Facility Generating Capacity	600
TUCO to Yoakum to Hobbs Plant Transmission Line
Capital Commitments [Abstract]
Voltage capacity for transmission line (in kV) | kV	345
Hobbs Plant to China Draw Transmission Line
Capital Commitments [Abstract]
Voltage capacity for transmission line (in kV) | kV	345