Jointly-Owned Facilities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Jul. 06, 2016
4CA
Interests in jointly-owned facilities
Plant in Service	$ 110,000
Accumulated Depreciation	79,000
Construction work in progress	$ 30,000
Palo Verde Units 1 and 3 | ARIZONA PUBLIC SERVICE COMPANY
Interests in jointly-owned facilities
Percent Owned	29.10%
Plant in Service	$ 1,770,324
Accumulated Depreciation	1,080,072
Construction work in progress	$ 17,615
Palo Verde Unit 2 | ARIZONA PUBLIC SERVICE COMPANY
Interests in jointly-owned facilities
Percent Owned	16.80%
Plant in Service	$ 581,572
Accumulated Depreciation	360,757
Construction work in progress	$ 9,717
Palo Verde Common | ARIZONA PUBLIC SERVICE COMPANY
Interests in jointly-owned facilities
Percent Owned	28.00%
Plant in Service	$ 672,799
Accumulated Depreciation	242,649
Construction work in progress	62,479
Palo Verde Sale Leaseback | ARIZONA PUBLIC SERVICE COMPANY
Interests in jointly-owned facilities
Plant in Service	351,050
Accumulated Depreciation	237,535
Construction work in progress	$ 0
Four Corners Generating Station | ARIZONA PUBLIC SERVICE COMPANY
Interests in jointly-owned facilities
Percent Owned	63.00%
Plant in Service	$ 934,837
Accumulated Depreciation	578,924
Construction work in progress	$ 248,072
Navajo Generating Station Units 1, 2 and 3 | ARIZONA PUBLIC SERVICE COMPANY
Interests in jointly-owned facilities
Percent Owned	14.00%
Plant in Service	$ 279,629
Accumulated Depreciation	176,931
Construction work in progress	$ 5,761
Cholla Common Facilities | ARIZONA PUBLIC SERVICE COMPANY
Interests in jointly-owned facilities
Percent Owned	63.30%
Plant in Service	$ 159,707
Accumulated Depreciation	58,276
Construction work in progress	$ 806
ANPP 500kV System | ARIZONA PUBLIC SERVICE COMPANY
Interests in jointly-owned facilities
Percent Owned	33.60%
Plant in Service	$ 127,970
Accumulated Depreciation	38,610
Construction work in progress	$ 2,291
Navajo Southern System | ARIZONA PUBLIC SERVICE COMPANY
Interests in jointly-owned facilities
Percent Owned	22.50%
Plant in Service	$ 62,135
Accumulated Depreciation	20,491
Construction work in progress	$ 334
Palo Verde — Yuma 500kV System | ARIZONA PUBLIC SERVICE COMPANY
Interests in jointly-owned facilities
Percent Owned	19.00%
Plant in Service	$ 13,699
Accumulated Depreciation	5,368
Construction work in progress	$ 408
Four Corners Switchyards | ARIZONA PUBLIC SERVICE COMPANY
Interests in jointly-owned facilities
Percent Owned	51.30%
Plant in Service	$ 39,850
Accumulated Depreciation	10,474
Construction work in progress	$ 1,044
Phoenix — Mead System | ARIZONA PUBLIC SERVICE COMPANY
Interests in jointly-owned facilities
Percent Owned	17.10%
Plant in Service	$ 39,330
Accumulated Depreciation	13,725
Construction work in progress	$ 85
Palo Verde — Rudd 500kV System | ARIZONA PUBLIC SERVICE COMPANY
Interests in jointly-owned facilities
Percent Owned	50.00%
Plant in Service	$ 91,904
Accumulated Depreciation	19,818
Construction work in progress	$ 227
Morgan — Pinnacle Peak System | ARIZONA PUBLIC SERVICE COMPANY
Interests in jointly-owned facilities
Percent Owned	65.20%
Plant in Service	$ 140,374
Accumulated Depreciation	13,557
Construction work in progress	$ 0
Round Valley System | ARIZONA PUBLIC SERVICE COMPANY
Interests in jointly-owned facilities
Percent Owned	50.00%
Plant in Service	$ 515
Accumulated Depreciation	127
Construction work in progress	$ 0
Palo Verde — Morgan System | ARIZONA PUBLIC SERVICE COMPANY
Interests in jointly-owned facilities
Percent Owned	85.80%
Plant in Service	$ 125,908
Accumulated Depreciation	1,326
Construction work in progress	$ 28,949
Hassayampa — North Gila System | ARIZONA PUBLIC SERVICE COMPANY
Interests in jointly-owned facilities
Percent Owned	80.00%
Plant in Service	$ 142,541
Accumulated Depreciation	3,231
Construction work in progress	$ 0
Cholla 500kV Switchyard | ARIZONA PUBLIC SERVICE COMPANY
Interests in jointly-owned facilities
Percent Owned	85.70%
Plant in Service	$ 5,078
Accumulated Depreciation	1,201
Construction work in progress	$ 0
Saguaro 500kV Switchyard | ARIZONA PUBLIC SERVICE COMPANY
Interests in jointly-owned facilities
Percent Owned	75.00%
Plant in Service	$ 20,456
Accumulated Depreciation	12,426
Construction work in progress	$ 2
Cholla common construction facilities | ARIZONA PUBLIC SERVICE COMPANY
Interests in jointly-owned facilities
Percent Owned	50.50%
El Paso's Interest in Four Corners | 4CA
Interests in jointly-owned facilities
Ownership interest acquired	7.00%	7.00%