Balance Sheet Components (Tables)

6 Months Ended

Jun. 30, 2021

Balance Sheet Related Disclosures [Abstract]

Materials and Supplies, Fuel Stock and Stored Natural Gas

Inventories of materials and supplies, fuel stock and stored natural gas are recorded at average cost for our regulated operations and the lower of cost or net realizable value for our non-regulated operations and consisted of the following as of June 30, 2021 and December 31, 2020 (dollars in thousands):

	June 30,		December 31,
	2021		2020
Materials and supplies	$	57,068	$	53,258
Fuel stock		5,780		4,658
Stored natural gas		19,930		9,535
Total	$	82,778	$	67,451

Schedule of Other Current Assets

Other current assets consisted of the following as of June 30, 2021 and December 31, 2020 (dollars in thousands):

	June 30,		December 31,
	2021		2020
Collateral posted for derivative instruments after netting with outstanding    derivative liabilities	$	25,089	$	4,336
Prepayments		22,444		24,411
Income taxes receivable		25,945		49,814
Other		9,662		6,324
Total	$	83,140	$	84,885

Schedule of Net Utility Property Recorded at Original Cost Net of Accumulated Depreciation

Net utility property, which is recorded at original cost net of accumulated depreciation, consisted of the following as of June 30, 2021 and December 31, 2020 (dollars in thousands):

	June 30,		December 31,
	2021		2020
Utility plant in service	$	6,980,002	$	6,809,797
Construction work in progress		185,011		175,767
Total		7,165,013		6,985,564
Less: Accumulated depreciation and amortization		2,064,251		1,993,952
Total net utility property	$	5,100,762	$	4,991,612

Other Property and Investments-Net and Other Non-Current Assets

Other property and investments-net and other non-current assets consisted of the following as of June 30, 2021 and December 31, 2020 (dollars in thousands):

	June 30,		December 31,
	2021		2020
Operating lease ROU assets	$	70,941	$	71,891
Equity investments		69,921		59,318
Finance lease ROU assets		45,518		47,338
Non-utility property		18,925		19,508
Notes receivable		14,803		14,454
Investment in affiliated trust		11,547		11,547
Deferred compensation assets		9,660		9,174
Assets held for sale (1)		—		3,462
Other		19,749		26,947
Total	$	261,064	$	263,639

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

Other Current Liabilities

Other current liabilities consisted of the following as of June 30, 2021 and December 31, 2020 (dollars in thousands):

	June 30, 2021		December 31, 2020
Accrued taxes other than income taxes	$	42,117	$	45,099
Derivative liabilities		33,276		14,008
Employee paid time off accruals		28,998		26,495
Accrued interest		16,594		17,083
Pensions and other postretirement benefits		12,429		11,987
Other		38,271		35,159
Total other current liabilities	$	171,685	$	149,831

Schedule of Other Non-Current Liabilities and Deferred Credits

Other non-current liabilities and deferred credits consisted of the following as of June 30, 2021 and December 31, 2020 (dollars in thousands):

	June 30, 2021		December 31, 2020
Operating lease liabilities	$	68,820	$	67,716
Finance lease liabilities		47,273		48,815
Deferred investment tax credits		29,590		29,866
Asset retirement obligations		16,734		17,194
Derivative liabilities		4,426		37,427
Other		15,700		13,981
Total	$	182,543	$	214,999

Schedule of Regulatory Assets and Liabilities

Regulatory assets and liabilities consisted of the following as of June 30, 2021 and December 31, 2020 (dollars in thousands):

	June 30, 2021				December 31, 2020
	Current		Non-Current		Current		Non-Current
Regulatory Assets
Energy commodity derivatives	$	5,652	$	1,410	$	2,073	$	5,722
Decoupling surcharge		9,768		13,911		7,123		17,123
Pension and other postretirement benefit plans		—		194,005		—		198,746
Interest rate swaps		—		197,302		—		214,851
Deferred income taxes (1)		—		238,234		—		108,517
Settlement with Coeur d'Alene Tribe		—		39,484		—		40,043
AFUDC above FERC allowed rate		—		48,961		—		47,393
Demand side management programs		—		1,449		—		3,814
Utility plant to be abandoned		—		27,599		—		28,916
COVID-19 deferrals		—		14,292		—		8,166
Other regulatory assets		11,754		93,448		4,477		77,152
Total regulatory assets	$	27,174	$	870,095	$	13,673	$	750,443
Regulatory Liabilities
Income tax related liabilities (1)	$	45,431	$	485,165	$	14,952	$	399,677
Deferred power costs		14,996		13,118		20,299		17,570
Decoupling rebate		849		3,754		1,447		1,519
Utility plant retirement costs		—		336,940		—		325,832
Interest rate swaps		—		15,637		—		15,046
COVID-19 deferrals		—		12,680		—		10,949
Other regulatory liabilities		8,900		15,149		9,737		14,227
Total regulatory liabilities	$	70,176	$	882,443	$	46,435	$	784,820

(1) In 2021, the Company received regulatory approval in all jurisdictions to change to flow-through tax treatment of certain basis adjustments, which was $127.5 million.