Balance Sheet Components Balance Sheet Components (Tables)

3 Months Ended

Mar. 31, 2020

Balance Sheet Related Disclosures [Abstract]

Schedule of Other Current Assets [Table Text Block]

Other current assets consisted of the following as of March 31, 2020 and December 31, 2019 (dollars in thousands):

	March 31,		December 31,
	2020		2019
Collateral posted for derivative instruments after netting with outstanding derivative liabilities	$	2,470	$	4,434
Prepayments	22,569		19,652
Income taxes receivable	—		11,047
Other	5,289		5,009
Total	$	30,328	$	40,142

Schedule of Inventory, Current [Table Text Block]

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 market for our non-regulated operations and consisted of the following as of March 31, 2020 and December 31, 2019 (dollars in thousands):

	March 31,		December 31,
	2020		2019
Materials and supplies	$	49,007	$	47,402
Fuel stock	4,740		4,875
Stored natural gas	2,934		14,306
Total	$	56,681	$	66,583

Public Utility Property, Plant, and Equipment [Table Text Block]

Net utility property consisted of the following as of March 31, 2020 and December 31, 2019 (dollars in thousands):

	March 31,		December 31,
	2020		2019
Utility plant in service	$	6,521,033	$	6,462,993
Construction work in progress	189,827		164,941
Total	6,710,860		6,627,934
Less: Accumulated depreciation and amortization	1,868,542		1,830,927
Total net utility property	$	4,842,318	$	4,797,007

Schedule of Other Current Assets [Table Text Block]

Other property and investments-net and other non-current assets consisted of the following as of March 31, 2020 and December 31, 2019 (dollars in thousands):

	March 31,		December 31,
	2020		2019
Operating lease ROU assets	$	65,303	$	69,746
Finance lease ROU assets	50,069		50,980
Non-utility property	26,511		27,159
Equity investments	51,467		51,258
Investment in affiliated trust	11,547		11,547
Notes receivable	14,970		14,060
Deferred compensation assets	8,670		8,948
Other	25,614		23,394
Total	$	254,151	$	257,092

Other Current Liabilities [Table Text Block]

Other current liabilities consisted of the following as of March 31, 2020 and December 31, 2019 (dollars in thousands):

	March 31,		December 31,
	2020		2019
Accrued taxes other than income taxes	$	48,980	$	36,965
Employee paid time off accruals	24,084		22,343
Accrued interest	31,033		16,486
Current portion of pensions and other postretirement benefits	9,811		8,826
Income taxes payable	5,199		298
Derivative liabilities	27,409		10,928
Other current liabilities	27,770		35,133
Total other current liabilities	$	174,286	$	130,979

Other Noncurrent Liabilities [Table Text Block]

Other non-current liabilities and deferred credits consisted of the following as of March 31, 2020 and December 31, 2019 (dollars in thousands):

	March 31,		December 31,
	2020		2019
Operating lease liabilities	$	62,145	$	65,565
Finance lease liabilities	51,016		51,750
Deferred investment tax credits	30,588		30,444
Asset retirement obligations	20,263		20,338
Derivative liabilities	60,278		19,685
Other	13,374		13,407
Total	$	237,664	$	201,189

Schedule Of Regulated Asset And Liability [Table Text Block]

Regulatory assets and liabilities consisted of the following as of March 31, 2020 and December 31, 2019 (dollars in thousands):

	March 31, 2020				December 31, 2019
	Current		Non-Current		Current		Non-Current
Regulatory Assets
Energy commodity derivatives	$	78	$	—	$	6,310	$	264
Decoupling surcharge	10,927		15,504		12,098		14,806
Pension and other postretirement benefit plans	—		206,112		—		208,754
Interest rate swaps	—		246,566		—		168,594
Deferred income taxes	—		96,525		—		95,752
Settlement with Coeur d'Alene Tribe	—		41,005		—		41,332
AFUDC above FERC allowed rate	—		41,333		—		40,749
Demand side management programs	—		8,670		—		12,170
Utility plant to be abandoned	—		31,678		—		31,291
Other regulatory assets	2,052		63,473		3,443		57,090
Total regulatory assets	$	13,057	$	750,866	$	21,851	$	670,802

	March 31, 2020				December 31, 2019
	Current		Non-Current		Current		Non-Current
Regulatory Liabilities
Income tax related liabilities	$	23,975	$	404,046	$	23,803	$	407,549
Deferred natural gas costs	5,449		—		3,189		—
Deferral power costs	23,595		20,716		14,155		23,544
Decoupling rebate	363		5,972		255		2,398
Provision for rate refund (Washington remand case)	8,490		—		3,565		—
Utility plant retirement costs	—		317,203		—		312,403
Interest rate swaps	—		16,136		—		17,088
Other regulatory liabilities	4,464		19,303		6,748		12,454
Total regulatory liabilities	$	66,336	$	783,376	$	51,715	$	775,436