Fair Value (Tables)

3 Months Ended

Mar. 31, 2019

Fair Value Disclosures [Abstract]

Fair Value Inputs, Liabilities, Quantitative Information [Table Text Block]

The following table presents the quantitative information which was used to estimate the fair values of the Level 3 assets and liabilities above as of March 31, 2019 (dollars in thousands):

	Fair Value (Net) at
	March 31, 2019			Valuation Technique	Unobservable Input	Range
Power exchange agreement	$	(612	)	Surrogate facility pricing	O&M charges	$40.05-$52.59/MWh (1)
					Transaction volumes	28,860 MWhs
Natural gas exchange agreement	$	(2,104	)	Internally derived weighted average cost of gas	Forward purchase prices	$1.70 - $2.98/mmBTU
					Forward sales prices	$1.63 - $4.11/mmBTU
					Purchase volumes	270,000 - 310,000 mmBTUs
					Sales volumes	60,000 - 310,000 mmBTUs

Fair Value of Assets And Liabilities Measured on Recurring Basis

	Level 1		Level 2		Level 3		Counterparty and Cash Collateral Netting (1)			Total
March 31, 2019
Assets:
Energy commodity derivatives	$	—	$	31,363	$	—	$	(31,113	)	$	250
Level 3 energy commodity derivatives:
Natural gas exchange agreement	—		—		123		(123		)	—
Foreign currency exchange derivatives	—		15		—		(15		)	—
Interest rate swap derivatives	—		5,090		—		(2,284		)	2,806
Deferred compensation assets:
Mutual Funds:
Fixed income securities (2)	1,758		—		—		—			1,758
Equity securities (2)	6,456		—		—		—			6,456
Total	$	8,214	$	36,468	$	123	$	(33,535	)	$	11,270
Liabilities:
Energy commodity derivatives	$	—	$	68,668	$	—	$	(66,030	)	$	2,638
Level 3 energy commodity derivatives:
Natural gas exchange agreement	—		—		2,227		(123		)	2,104
Power exchange agreement	—		—		612		—			612
Foreign currency exchange derivatives	—		15		—		(15		)	—
Interest rate swap derivatives	—		15,210		—		(5,144		)	10,066
Total	$	—	$	83,893	$	2,839	$	(71,312	)	$	15,420

	Level 1		Level 2		Level 3		Counterparty and Cash Collateral Netting (1)			Total
December 31, 2018
Assets:
Energy commodity derivatives	$	—	$	36,252	$	—	$	(35,982	)	$	270
Level 3 energy commodity derivatives:
Natural gas exchange agreement	—		—		31		(31		)	—
Interest rate swap derivatives	—		10,566		—		(440		)	10,126
Deferred compensation assets:
Mutual Funds:
Fixed income securities (2)	1,745		—		—		—			1,745
Equity securities (2)	6,157		—		—		—			6,157
Total	$	7,902	$	46,818	$	31	$	(36,453	)	$	18,298
Liabilities:
Energy commodity derivatives	$	—	$	89,283	$	—	$	(87,199	)	$	2,084
Level 3 energy commodity derivatives:
Natural gas exchange agreement	—		—		2,805		(31		)	2,774
Power exchange agreement	—		—		2,488		—			2,488
Power option agreement	—		—		1		—			1
Foreign currency exchange derivatives	—		45		—		—			45
Interest rate swap derivatives	—		7,831		—		(970		)	6,861
Total	$	—	$	97,159	$	5,294	$	(88,200	)	$	14,253

(1) The Company is permitted to net derivative assets and derivative liabilities with the same counterparty when a legally enforceable master netting agreement exists. In addition, the Company nets derivative assets and derivative liabilities against any payables and receivables for cash collateral held or placed with these same counterparties.

(2) These assets are included in other property and investments-net and other non-current assets on the Condensed Consolidated Balance Sheets.

Reconciliation for All Assets Measured At Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Level 3)

	Natural Gas Exchange Agreement			Power Exchange Agreement			Total
Three months ended March 31, 2019:
Balance as of January 1, 2019	$	(2,774	)	$	(2,488	)	$	(5,262	)
Total gains or (losses) (realized/unrealized):
Included in regulatory assets/liabilities (1)	8,977			(1,018		)	7,959
Settlements	(8,307		)	2,894			(5,413		)
Ending balance as of March 31, 2019 (2)	$	(2,104	)	$	(612	)	$	(2,716	)

	Natural Gas Exchange Agreement			Power Exchange Agreement			Total
Three months ended March 31, 2018:
Balance as of January 1, 2018	$	(3,164	)	$	(13,245	)	$	(16,409	)
Total gains or (losses) (realized/unrealized):
Included in regulatory assets/liabilities (1)	203			(1,877		)	(1,674		)
Settlements	156			4,959			5,115
Ending balance as of March 31, 2018 (2)	$	(2,805	)	$	(10,163	)	$	(12,968	)

(1) All gains and losses are included in other regulatory assets and liabilities. There were no gains and losses included in either net income or other comprehensive income during any of the periods presented in the table above.

(2) There were no purchases, issuances or transfers from other categories of any derivatives instruments during the periods presented in the table above.

Carrying Value and Estimated Fair Value of Financial Instruments

The following table sets forth the carrying value and estimated fair value of the Company’s financial instruments not reported at estimated fair value on the Condensed Consolidated Balance Sheets as of March 31, 2019 and December 31, 2018 (dollars in thousands):

	March 31, 2019				December 31, 2018
	Carrying Value		Estimated Fair Value		Carrying Value		Estimated Fair Value
Long-term debt (Level 2)	$	1,053,500	$	1,155,199	$	1,053,500	$	1,142,292
Long-term debt (Level 3)	767,000		734,742		767,000		734,742
Snettisham finance lease obligation (Level 3)	56,545		56,900		57,210		55,600
Long-term debt to affiliated trusts (Level 3)	51,547		38,145		51,547		38,145