Balance Sheet Components - Other Property and Investments-Net and Other Non-current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2021		Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Operating lease ROU assets	$ 70,578		$ 71,891
Equity investments	83,496		59,318
Finance lease ROU assets	44,607		47,338
Non-utility property	19,248		19,508
Notes receivable	14,759		14,454
Investment in affiliated trust	11,547		11,547
Deferred compensation assets	9,917		9,174
Assets held for sale	0	[1]	3,462
Other	23,848		26,947
Total	$ 278,000		$ 263,639

[1] During the second quarter of 2021, the Company sold certain subsidiary assets associated with the Spokane Steam Plant.