Fair Value (Tables)

3 Months Ended

Mar. 31, 2018

Fair Value Inputs, Liabilities, Quantitative Information [Line Items]

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, 2018 (dollars in thousands):

	Fair Value (Net) at
	March 31, 2018			Valuation Technique	Unobservable Input	Range
Power exchange agreement	$	(10,163	)	Surrogate facility pricing	O&M charges	$38.87-$45.20/MWh (1)
					Escalation factor	5% - 2018 to 2019
					Transaction volumes	42,682 - 396,984 MWhs
Power option agreement	$	(5	)	Black-Scholes- Merton	Strike price	$34.01/MWh - 2018
						$40.42/MWh - 2019
					Delivery volumes	94,221 - 128,491 MWhs
Natural gas exchange agreement	$	(2,805	)	Internally derived weighted average cost of gas	Forward purchase prices	$1.41 - $2.00/mmBTU
					Forward sales prices	$1.33 - $2.85/mmBTU
					Purchase volumes	115,000 - 310,000 mmBTUs
					Sales volumes	60,000 - 310,000 mmBTUs

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, 2018 and December 31, 2017 (dollars in thousands):

	March 31, 2018				December 31, 2017
	Carrying Value		Estimated Fair Value		Carrying Value		Estimated Fair Value
Long-term debt (Level 2)	$	951,000	$	1,077,127	$	951,000	$	1,067,783
Long-term debt (Level 3)	767,000		768,947		767,000		810,598
Snettisham capital lease obligation (Level 3)	59,111		58,700		59,745		61,700
Long-term debt to affiliated trusts (Level 3)	51,547		40,722		51,547		41,882

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, 2018
Assets:
Energy commodity derivatives	$	—	$	60,025	$	—	$	(59,064	)	$	961
Level 3 energy commodity derivatives:
Natural gas exchange agreement	—		—		47		(47		)	—
Foreign currency exchange derivatives	—		22		—		(6		)	16
Interest rate swap derivatives	—		14,715		—		(1,631		)	13,084
Deferred compensation assets:
Mutual Funds:
Fixed income securities (2)	1,663		—		—		—			1,663
Equity securities (2)	6,810		—		—		—			6,810
Total	$	8,473	$	74,762	$	47	$	(60,748	)	$	22,534
Liabilities:
Energy commodity derivatives	$	—	$	77,218	$	—	$	(75,660	)	$	1,558
Level 3 energy commodity derivatives:
Natural gas exchange agreement	—		—		2,852		(47		)	2,805
Power exchange agreement	—		—		10,163		—			10,163
Power option agreement	—		—		5		—			5
Foreign currency exchange derivatives	—		6		—		(6		)	—
Interest rate swap derivatives	—		55,731		—		(29,261		)	26,470
Total	$	—	$	132,955	$	13,020	$	(104,974	)	$	41,001

	Level 1		Level 2		Level 3		Counterparty and Cash Collateral Netting (1)			Total
December 31, 2017
Assets:
Energy commodity derivatives	$	—	$	43,814	$	—	$	(42,550	)	$	1,264
Level 3 energy commodity derivatives:
Natural gas exchange agreement	—		—		183		(183		)	—
Foreign currency exchange derivatives	—		32		—		(1		)	31
Interest rate swap derivatives	—		7,477		—		(2,574		)	4,903
Deferred compensation assets:
Mutual Funds:
Fixed income securities (2)	1,638		—		—		—			1,638
Equity securities (2)	6,631		—		—		—			6,631
Total	$	8,269	$	51,323	$	183	$	(45,308	)	$	14,467
Liabilities:
Energy commodity derivatives	$	—	$	71,342	$	—	$	(69,988	)	$	1,354
Level 3 energy commodity derivatives:
Natural gas exchange agreement	—		—		3,347		(183		)	3,164
Power exchange agreement	—		—		13,245		—			13,245
Power option agreement	—		—		19		—			19
Foreign currency exchange derivatives	—		1		—		(1		)	—
Interest rate swap derivatives	—		73,513		—		(37,544		)	35,969
Total	$	—	$	144,856	$	16,611	$	(107,716	)	$	53,751

(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 trading securities and 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			Power Option Agreement			Total
Three months ended March 31, 2018:
Balance as of January 1, 2018	$	(3,164	)	$	(13,245	)	$	(19	)	$	(16,428	)
Total gains or (losses):
Included in regulatory assets/liabilities (1)	203			(1,877		)	14			(1,660		)
Settlements	156			4,959			—			5,115
Ending balance as of March 31, 2018 (2)	$	(2,805	)	$	(10,163	)	$	(5	)	$	(12,973	)
Three months ended March 31, 2017:
Balance as of January 1, 2017	$	(5,885	)	$	(13,449	)	$	(76	)	$	(19,410	)
Total gains or (losses):
Included in regulatory assets/liabilities (1)	2,012			(4,493		)	(190		)	(2,671		)
Settlements	(405		)	3,523			—			3,118
Ending balance as of March 31, 2017 (2)	$	(4,278	)	$	(14,419	)	$	(266	)	$	(18,963	)

(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.