Jointly Owned Electric Facilities (Tables)

12 Months Ended

Dec. 31, 2020

Jointly Owned Utility Plant Net Ownership Amount [Abstract]

Schedule of Utility Plant in Service for Colstrip And Accumulated Depreciation

The Company’s share of utility plant in service for Colstrip and accumulated depreciation (inclusive of the ARO assets and accumulated amortization) were as follows as of December 31 (dollars in thousands):

	2020			2019
Utility plant in service	$	391,922		$	387,860
Accumulated depreciation		(284,282	)		(268,637	)