Regulation Regulation Narrative - Texas (Details)																		3 Months Ended			6 Months Ended
	Jun. 01, 2019 USD ($)	May 01, 2019 USD ($)	Apr. 30, 2019 USD ($)	Mar. 28, 2019 USD ($)	Feb. 22, 2019 USD ($)	Jan. 25, 2019 USD ($)	Jan. 17, 2019 USD ($)	Nov. 01, 2018	May 01, 2018 USD ($)	Apr. 01, 2018	Mar. 01, 2018 USD ($)	Feb. 15, 2018 USD ($)	Jan. 01, 2018	Dec. 18, 2017 USD ($)	Nov. 01, 2017	Aug. 01, 2017	Jun. 29, 2017 USD ($)	Jun. 30, 2019 USD ($) MW	Mar. 31, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2019 USD ($) MW	Jun. 30, 2018 USD ($)	May 09, 2019 MW	Mar. 31, 2019 USD ($)	Mar. 20, 2018 MW	Jun. 08, 2015 MW
Public Utilities, General Disclosures [Line Items]
Payments to Acquire Investments to be Held in Decommissioning Trust Fund																					$ 54,258,000	$ 47,896,000
PUCT
Public Utilities, General Disclosures [Line Items]
Period to file application with regulatory agency																					4 months
Fuel Over And Under Materiality Threshold Percentage																		4.00%			4.00%
Fuel Reconciliation Period																		3 months			36 months
Deferred Fuel Costs Over Collected																		$ 20,300,000			$ 20,300,000
Reconcilable Fuel Expense																		$ 12,000,000.0			$ 12,000,000.0			$ 361,500,000
Community Solar at Newman | PUCT
Public Utilities, General Disclosures [Line Items]
Electric Capacity | MW																		10			10
PUCT Docket No. 46831
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Return on Equity, Percentage														9.65%
Regulatory Assets														$ 3,400,000
Surcharge Or Refund Period														3 years
Minimum Distributive Generation Charge														$ 30.00
Payments to Acquire Investments to be Held in Decommissioning Trust Fund														2,100,000
Public Utilities, Increase (Decrease) In Requested Depreciation Expense														(1,900,000)
PUCT Docket No. 46831 | Four Corners decommissioning
Public Utilities, General Disclosures [Line Items]
Decommissioning Costs Increase (Decrease)														5,500,000
Remaining Recovery Period of Regulatory Assets for which No Return on Investment During Recovery Period is Provided																7 years
PUCT Docket No. 46831 | Non-Fuel Base Rate
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount														$ 14,500,000
Public Utilities, Regulatory Rate Making Impact | PUCT
Public Utilities, General Disclosures [Line Items]
Period To Relate Back New Rates													167 days
PUCT Docket No. 48124
Public Utilities, General Disclosures [Line Items]
Surcharge Or Refund Period										1 year
Public Utilities, Requested Rate Increase (Decrease), Amount											$ (22,700,000)								$ (4,300,000)
Tax benefit refund period																			3 months
PUCT Docket No. 49251
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount					$ (4,300,000)
PUCT Docket No. 47125 | 2016 Energy Efficiency Programs
Public Utilities, General Disclosures [Line Items]
Public Utilities Approved Performance Incentive Bonus Related To Energy Efficiency Program												$ 800,000
PUCT Docket No. 48332 | 2017 Energy Efficiency Programs
Public Utilities, General Disclosures [Line Items]
Public Utilities Approved Performance Incentive Bonus Related To Energy Efficiency Program							$ 900,000
Public Utilities Requested Performance Incentive Bonus Related To Energy Efficiency Program									$ 1,000,000.0
PUCT Docket No. 49496 | 2018 Energy Efficiency Programs
Public Utilities, General Disclosures [Line Items]
Public Utilities Requested Performance Incentive Bonus Related To Energy Efficiency Program		$ 800,000
PUCT Docket No. 47692 | Fixed Fuel Factor
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Percentage															(19.00%)
PUCT Docket No. 48264 | Fixed Fuel Factor
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Percentage									(29.00%)
PUCT Docket No. 48781 | Fixed Fuel Factor
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Percentage								(6.99%)
PUCT Docket No. 49482
Public Utilities, General Disclosures [Line Items]
Surcharge Or Refund Period	4 months
Fuel Reconciliation Period	36 months
Deferred fuel costs over-collected, including interest, amount	$ 19,400,000
PUCT Docket No. 46308
Public Utilities, General Disclosures [Line Items]
Fuel Reconciliation Period																	36 months
Reconcilable Fuel Expense																	$ 436,600,000
Public Utilities, Fuel Reconciliation Effect, Net Amount																				$ 5,000,000.0
Palo Verde Performance Award Period																	3 years
PUCT Docket No. 44800 | Community Solar At Montana Power Station
Public Utilities, General Disclosures [Line Items]
Electric Capacity | MW																										3
Number Of Customers																		1,500			1,500
PUCT Docket No. 48181 | Community Solar at Newman
Public Utilities, General Disclosures [Line Items]
Electric Capacity | MW																							2
Electric capacity, requested | MW																									2
PUCT Docket No. 49148
Public Utilities, General Disclosures [Line Items]
Recovery period for property, plant or equipment placed into service						24 months
Public Utilities, Requested Rate Increase (Decrease), Amount						$ 8,200,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount			$ 8,100,000
PUCT Docket No. 49395
Public Utilities, General Disclosures [Line Items]
Recovery period for property, plant or equipment placed into service				27 months
Public Utilities, Requested Rate Increase (Decrease), Amount				$ 7,900,000