Other Income and Other Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Other income:
Interest income	$ 1,602	$ 2,956	$ 5,236	$ 8,988
Investment gains - net	0	0	0	2,594
Miscellaneous	4	2	48	146
Total other income	12,083	13,881	36,719	42,888
Other expense:
Non-operating costs	(2,973)	(2,453)	(9,013)	(7,401)
Investment gains (losses) — net	(704)	(291)	(1,478)	0
Miscellaneous	(2,505)	(3,094)	(4,728)	(7,025)
Total other expense	(6,182)	(5,838)	(15,219)	(14,426)
APS
Other income:
Interest income	1,118	2,403	3,645	6,927
Miscellaneous	2	2	40	146
Total other income	11,597	13,328	35,120	38,233
Other expense:
Non-operating costs	(1,892)	(1,906)	(7,284)	(6,501)
Miscellaneous	(304)	(893)	(2,523)	(4,825)
Total other expense	(2,196)	(2,799)	(9,807)	(11,326)
SCR deferral
Other income:
Debt return on Four Corners SCR deferrals (Note 4)	4,091	4,260	12,266	11,649
SCR deferral | APS
Other income:
Debt return on Four Corners SCR deferrals (Note 4)	4,091	4,260	12,266	11,649
Ocotillo deferral
Other income:
Debt return on Four Corners SCR deferrals (Note 4)	6,386	6,663	19,169	19,511
Ocotillo deferral | APS
Other income:
Debt return on Four Corners SCR deferrals (Note 4)	$ 6,386	$ 6,663	$ 19,169	$ 19,511