Regulatory and Rate Matters - Application For a New 345 KV Transmission Line and Western Spirit Line (Details) $ in Millions	Jun. 03, 2019 MW	May 01, 2019 USD ($) kv	Aug. 10, 2018 USD ($) kv MW	Mar. 21, 2018 MW
KV Transmission Line
Public Utilities, General Disclosures [Line Items]
Transmission line and associated facilities generation capacity (in kilovolts) | kv			345
Solar generation capacity (in megawatts) | MW			166
Estimated cost of project			$ 85.0
Facebook Data Center
Public Utilities, General Disclosures [Line Items]
Estimated cost of project			$ 39.0
Estimated cost of project, percentage			46.00%
Facebook Data Center | Avangrid Renewables, LLC
Public Utilities, General Disclosures [Line Items]
Solar generation capacity (in megawatts) | MW				166
Western Spirit Line
Public Utilities, General Disclosures [Line Items]
Transmission line and associated facilities generation capacity (in kilovolts) | kv		345
Estimated cost of project		$ 285.0
Estimated self-fund amount under agreement		$ 75.0
La Joya Wind | KV Transmission Line
Public Utilities, General Disclosures [Line Items]
Solar generation capacity (in megawatts) | MW	140		140