Other Income and Other Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Other income:
Interest income	$ 3,277	$ 2,302
Miscellaneous	8	23
Total other income	12,569	7,169
Other expense:
Non-operating costs	(2,658)	(2,704)
Non-operating costs	60	(238)
Miscellaneous	(2,186)	(1,416)
Total other expense	(4,784)	(4,358)
APS
Other income:
Interest income	2,341	1,550
Miscellaneous	8	22
Total other income	11,633	6,416
Other expense:
Non-operating costs	(2,482)	(2,467)
Miscellaneous	(2,186)	(1,411)
Total other expense	(4,668)	(3,878)
SCR deferral
Other income:
Debt return on Four Corners SCR deferrals (Note 4)	3,140	4,844
SCR deferral | APS
Other income:
Debt return on Four Corners SCR deferrals (Note 4)	3,140	4,844
Ocotillo deferral
Other income:
Debt return on Four Corners SCR deferrals (Note 4)	6,144	0
Ocotillo deferral | APS
Other income:
Debt return on Four Corners SCR deferrals (Note 4)	$ 6,144	$ 0