Other Income and Other Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Other income:
Interest income	$ 1,687	$ 2,755	$ 3,635	$ 6,032
Investment gains - net	0	2,826	0	2,826
Miscellaneous	40	137	43	145
Total other income	12,207	16,670	24,636	29,239
Other expense:
Non-operating costs	(4,102)	(2,290)	(6,039)	(4,948)
Investment gains (losses) — net	(431)	0	(774)	60
Miscellaneous	(651)	(1,746)	(2,224)	(3,932)
Total other expense	(5,184)	(4,036)	(9,037)	(8,820)
APS
Other income:
Interest income	1,047	2,183	2,528	4,524
Miscellaneous	36	137	37	145
Total other income	11,563	13,272	23,523	24,905
Other expense:
Non-operating costs	(3,615)	(2,113)	(5,392)	(4,595)
Miscellaneous	(646)	(1,746)	(2,219)	(3,932)
Total other expense	(4,261)	(3,859)	(7,611)	(8,527)
SCR deferral
Other income:
Debt return on Four Corners SCR deferrals (Note 4)	4,089	4,249	8,175	7,389
SCR deferral | APS
Other income:
Debt return on Four Corners SCR deferrals (Note 4)	4,089	4,249	8,175	7,389
Ocotillo deferral
Other income:
Debt return on Four Corners SCR deferrals (Note 4)	6,391	6,703	12,783	12,847
Ocotillo deferral | APS
Other income:
Debt return on Four Corners SCR deferrals (Note 4)	$ 6,391	$ 6,703	$ 12,783	$ 12,847