Jointly-Owned Facilities (Details) - ARIZONA PUBLIC SERVICE COMPANY $ in Thousands	Dec. 31, 2018 USD ($)
Navajo Plant
Interests in jointly-owned facilities
Ownership interest by noncontrolling owners (as a percent)	14.00%
Palo Verde Units 1 and 3
Interests in jointly-owned facilities
Percent Owned	29.10%
Plant in Service	$ 1,887,729
Accumulated Depreciation	1,095,878
Construction work in progress	$ 25,185
Palo Verde Unit 2
Interests in jointly-owned facilities
Percent Owned	16.80%
Plant in Service	$ 638,419
Accumulated Depreciation	369,372
Construction work in progress	$ 20,852
Palo Verde Common
Interests in jointly-owned facilities
Percent Owned	28.00%
Plant in Service	$ 752,300
Accumulated Depreciation	277,414
Construction work in progress	39,995
Palo Verde Sale Leaseback
Interests in jointly-owned facilities
Plant in Service	351,050
Accumulated Depreciation	245,275
Construction work in progress	$ 0
Four Corners Generating Station
Interests in jointly-owned facilities
Percent Owned	63.00%
Plant in Service	$ 1,466,579
Accumulated Depreciation	544,308
Construction work in progress	$ 23,430
Cholla Common Facilities
Interests in jointly-owned facilities
Percent Owned	50.50%
Plant in Service	$ 183,390
Accumulated Depreciation	82,434
Construction work in progress	$ 893
ANPP 500kV System
Interests in jointly-owned facilities
Percent Owned	33.50%
Plant in Service	$ 129,587
Accumulated Depreciation	49,340
Construction work in progress	$ 2,705
Navajo Southern System
Interests in jointly-owned facilities
Percent Owned	26.70%
Plant in Service	$ 82,046
Accumulated Depreciation	30,464
Construction work in progress	$ 284
Palo Verde — Yuma 500kV System
Interests in jointly-owned facilities
Percent Owned	19.00%
Plant in Service	$ 15,304
Accumulated Depreciation	6,729
Construction work in progress	$ 530
Four Corners Switchyards
Interests in jointly-owned facilities
Percent Owned	63.10%
Plant in Service	$ 68,707
Accumulated Depreciation	15,436
Construction work in progress	$ 1,334
Phoenix — Mead System
Interests in jointly-owned facilities
Percent Owned	17.10%
Plant in Service	$ 39,329
Accumulated Depreciation	18,527
Construction work in progress	$ 44
Palo Verde — Rudd 500kV System
Interests in jointly-owned facilities
Percent Owned	50.00%
Plant in Service	$ 93,887
Accumulated Depreciation	25,573
Construction work in progress	$ 302
Morgan — Pinnacle Peak System
Interests in jointly-owned facilities
Percent Owned	64.60%
Plant in Service	$ 117,722
Accumulated Depreciation	16,744
Construction work in progress	$ 0
Round Valley System
Interests in jointly-owned facilities
Percent Owned	50.00%
Plant in Service	$ 515
Accumulated Depreciation	153
Construction work in progress	$ 0
Palo Verde — Morgan System
Interests in jointly-owned facilities
Percent Owned	87.90%
Plant in Service	$ 219,292
Accumulated Depreciation	6,660
Construction work in progress	$ 0
Hassayampa — North Gila System
Interests in jointly-owned facilities
Percent Owned	80.00%
Plant in Service	$ 142,541
Accumulated Depreciation	9,805
Construction work in progress	$ 0
Cholla 500kV Switchyard
Interests in jointly-owned facilities
Percent Owned	85.70%
Plant in Service	$ 5,078
Accumulated Depreciation	1,414
Construction work in progress	$ 38
Saguaro 500kV Switchyard
Interests in jointly-owned facilities
Percent Owned	60.00%
Plant in Service	$ 20,414
Accumulated Depreciation	12,790
Construction work in progress	$ 0
Kyrene — Knox System
Interests in jointly-owned facilities
Percent Owned	50.00%
Plant in Service	$ 578
Accumulated Depreciation	307
Construction work in progress	$ 0