Balance Sheet Components Balance Sheet Components (Tables)

3 Months Ended

Mar. 31, 2019

Balance Sheet Related Disclosures [Abstract]

Schedule of Other Current Assets [Table Text Block]

Other current assets consisted of the following as of March 31, 2019 and December 31, 2018 (dollars in thousands):

	March 31,		December 31,
	2019		2018
Collateral posted for derivative instruments after netting with outstanding derivative liabilities	$	37,347	$	26,809
Prepayments	16,647		17,536
Other	6,954		9,665
Total	$	60,948	$	54,010

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, 2019 and December 31, 2018 (dollars in thousands):

	March 31,		December 31,
	2019		2018
Materials and supplies	$	47,705	$	47,403
Fuel stock	4,930		4,869
Stored natural gas	8,719		11,609
Total	$	61,354	$	63,881

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

Net utility property consisted of the following as of March 31, 2019 and December 31, 2018 (dollars in thousands):

	March 31,		December 31,
	2019		2018
Utility plant in service	$	6,202,942	$	6,209,968
Construction work in progress	165,725		160,598
Total	6,368,667		6,370,566
Less: Accumulated depreciation and amortization	1,742,613		1,721,636
Total net utility property	$	4,626,054	$	4,648,930

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, 2019 and December 31, 2018 (dollars in thousands):

	March 31,		December 31,
	2019		2018
Operating lease ROU assets	$	70,834	$	—
Finance lease ROU assets	53,711		—
Non-utility property	29,557		31,355
Equity investments	32,967		29,257
Investment in affiliated trust	11,547		11,547
Notes receivable	11,161		11,073
Deferred compensation assets	8,675		8,400
Other	22,751		23,065
Total	$	241,203	$	114,697

Other Current Liabilities [Table Text Block]

Other current liabilities consisted of the following as of March 31, 2019 and December 31, 2018 (dollars in thousands):

	March 31,		December 31,
	2019		2018
Accrued taxes other than income taxes	$	49,206	$	36,858
Income taxes payable	20,368		141
Employee paid time off accruals	21,813		20,992
Accrued interest	30,315		16,704
Current portion of pensions and other postretirement benefits	9,503		9,151
Operating lease liabilities	4,120		—
Finance lease liabilities	2,695		—
Utility energy commodity derivative liabilities	4,035		3,908
Other current liabilities	33,399		32,604
Total other current liabilities	$	175,454	$	120,358

Other Noncurrent Liabilities [Table Text Block]

Other non-current liabilities and deferred credits consisted of the following as of March 31, 2019 and December 31, 2018 (dollars in thousands):

	March 31,		December 31,
	2019		2018
Operating lease liabilities	$	67,635	$	—
Finance lease liabilities	53,850		—
Deferred investment tax credits	31,383		29,725
Asset retirement obligations	18,455		18,266
Derivative liabilities	10,861		10,300
Other	13,564		12,740
Total	$	195,748	$	71,031

Schedule Of Regulated Asset And Liability [Table Text Block]

Regulatory assets and liabilities consisted of the following as of March 31, 2019 and December 31, 2018 (dollars in thousands):

	March 31, 2019				December 31, 2018
	Current		Non-Current		Current		Non-Current
Regulatory Assets
Energy commodity derivatives	$	28,159	$	11,862	$	41,428	$	16,866
Decoupling surcharge	6,782		8,395		3,408		17,501
Pension and other postretirement benefit plans	—		224,805		—		228,062
Interest rate swaps	—		138,327		—		133,854
Deferred income taxes	—		93,646		—		91,188
Settlement with Coeur d'Alene Tribe	—		42,316		—		42,643
Demand side management programs	—		15,064		—		19,674
Utility plant to be abandoned	—		24,477		—		24,334
Other regulatory assets	6,625		46,605		3,716		40,232
Total regulatory assets	$	41,566	$	605,497	$	48,552	$	614,354
Regulatory Liabilities
Income tax related liabilities	$	29,401	$	421,216	$	27,997	$	425,613
Deferred natural gas costs	1,253		—		40,713		—
Deferral power costs	12,555		26,106		25,072		16,933
Decoupling rebate	1,061		4,664		6,782		204
Utility plant retirement costs	—		300,373		—		297,379
Interest rate swaps	—		20,396		—		28,078
Other regulatory liabilities	11,194		13,478		12,645		12,494
Total regulatory liabilities	$	55,464	$	786,233	$	113,209	$	780,701