Other Income and Other Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Other income:
Interest income	$ 2,956	$ 2,694	$ 8,988	$ 7,695
Investment gains (losses) - net	0	0	2,594	0
Miscellaneous	2	22	146	50
Total other income	13,881	15,191	42,888	35,245
Other expense:
Non-operating costs	(2,453)	(2,647)	(7,401)	(8,832)
Investment gains (losses) — net	(291)	(716)	0	(1,445)
Miscellaneous	(3,094)	(2,377)	(7,025)	(4,171)
Total other expense	(5,838)	(5,740)	(14,426)	(14,448)
APS
Other income:
Interest income	2,403	2,037	6,927	5,091
Miscellaneous	2	22	146	50
Total other income	13,328	14,534	38,233	32,641
Other expense:
Non-operating costs	(1,906)	(2,448)	(6,501)	(7,965)
Miscellaneous	(893)	(378)	(4,825)	(2,167)
Total other expense	(2,799)	(2,826)	(11,326)	(10,132)
SCR deferral
Other income:
Debt return on Four Corners SCR deferrals (Note 4)	4,260	4,920	11,649	14,651
SCR deferral | APS
Other income:
Debt return on Four Corners SCR deferrals (Note 4)	4,260	4,920	11,649	14,651
Ocotillo deferral
Other income:
Debt return on Four Corners SCR deferrals (Note 4)	6,663	7,555	19,511	12,849
Ocotillo deferral | APS
Other income:
Debt return on Four Corners SCR deferrals (Note 4)	$ 6,663	$ 7,555	$ 19,511	$ 12,849