Commitments and Contingencies (Texas, Nuclear) (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Loss Contingencies [Line Items]
Guarantee Obligations, Estimated Exposure	$ 3,630,000	$ 2,878,000
Nuclear insurance liability limit per incident	13,440,000
Required nuclear liability insurance	450,000
Nuclear financial protection pool mandated by the Price-Anderson Act	13,000,000
Maximum assessment mandated by Price-Anderson Act per nuclear reactor for a nuclear incident	$ 127,000
Nuclear Insurance Financial Protection Pool, Maximum Assessment, Adminstrative Fee, As a Percent	5.00%
Maximum annual assessment payment mandated by Price-Anderson Act for a nuclear incident	$ 19,000
44% maximum assessment	44.00%
Nuclear Insurance Financial Protection Pool Nuclear Operator Maximum Annual Assessment	$ 8,000
Maximum liability per nuclear incident	112,000
Mutual property insurance additional blanket policy property coverage	1,250,000
Nuclear property insurance coverage limit per individual insured	1,500,000
Mutual Lost Revenue Insurance Maximum Weekly Recovery	2,520
Accidental outage weekly recovery limit for loss revenues from a nuclear industry mutual insurance company in the event of insurable loss	$ 1,980
Multiplier that the industry mutual insurance company may assess against insureds premium	10
The number of months a nuclear industry mutual insurance company will respond to retrospective premium adjustments	24 months
Number of years board of directors of industry mutual insurance company can adjust policy after policy expires	6 years
Nuclear Event [Member]
Loss Contingencies [Line Items]
Total nuclear property insurance coverage	$ 2,750,000
Mutual Lost Revenue Insurance Maximum Weekly Recovery	274,400
Accidental outage weekly recovery limit for loss revenues from a nuclear industry mutual insurance company in the event of insurable loss	215,600
Non-nuclear Event [Member]
Loss Contingencies [Line Items]
Total nuclear property insurance coverage	1,500,000
Mutual Lost Revenue Insurance Maximum Weekly Recovery	183,500
Accidental outage weekly recovery limit for loss revenues from a nuclear industry mutual insurance company in the event of insurable loss	144,000
Lignite Contract with Texas Westmoreland Coal Co. [Member] | Guarantee of Indebtedness of Others [Member]
Loss Contingencies [Line Items]
Guarantee Obligations, Estimated Exposure	$ 95,500