Income Taxes - Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Tabular reconciliation of the total amounts of unrecognized tax benefits, excluding interest and penalties, at the beginning and end of the year
Total unrecognized tax benefits, beginning of the year	$ 36,075	$ 34,447	$ 44,775
Additions for tax positions of the current year	2,937	2,695	2,175
Additions for tax positions of prior years	4,783	886	0
Reductions for tax positions of prior years for:
Changes in judgment	(1,829)	(1,953)	(10,244)
Settlements with taxing authorities	0	0	0
Lapses of applicable statute of limitations	0	0	(2,259)
Total unrecognized tax benefits, end of the year	41,966	36,075	34,447
ARIZONA PUBLIC SERVICE COMPANY
Tabular reconciliation of the total amounts of unrecognized tax benefits, excluding interest and penalties, at the beginning and end of the year
Total unrecognized tax benefits, beginning of the year	36,075	34,447	44,775
Additions for tax positions of the current year	2,937	2,695	2,175
Additions for tax positions of prior years	4,783	886	0
Reductions for tax positions of prior years for:
Changes in judgment	(1,829)	(1,953)	(10,244)
Settlements with taxing authorities	0	0	0
Lapses of applicable statute of limitations	0	0	(2,259)
Total unrecognized tax benefits, end of the year	$ 41,966	$ 36,075	$ 34,447