Fair Value (Tables)

12 Months Ended

Dec. 31, 2017

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 December 31, 2017 (dollars in thousands):



	Fair Value (Net) at
	December 31, 2017			Valuation Technique	Unobservable Input	Range
Power exchange agreement	$	(13,245	)	Surrogate facility	O&M charges	$38.87-$45.20/MWh (1)
				pricing	Escalation factor	5% - 2018 to 2019
					Transaction volumes	256,663 - 396,984 MWhs
Power option agreement	(19		)	Black-Scholes-	Strike price	$36.64/MWh - 2018
				Merton		$42.51/MWh - 2018
					Delivery volumes	94,221 - 190,339 MWhs
Natural gas exchange	(3,164		)	Internally derived	Forward purchase prices	$1.60 - $2.07/mmBTU
agreement				weighted-average	Forward sales prices	$1.56 - $2.98/mmBTU
				cost of gas	Purchase volumes	115,000 - 310,000 mmBTUs
					Sales volumes	60,000 - 310,000 mmBTUs

(1) The average O&M charges for the delivery year beginning in November 2017 are $41.95 per MWh.

Carrying Value and Estimated Fair Value of Financial Instruments



	2017				2016
	Carrying Value		Estimated Fair Value		Carrying Value		Estimated Fair Value
Long-term debt (Level 2)	$	951,000	$	1,067,783	$	951,000	$	1,048,661
Long-term debt (Level 3)	767,000		810,598		677,000		675,251
Snettisham capital lease obligation (Level 3)	59,745		61,700		62,160		62,800
Long-term debt to affiliated trusts (Level 3)	51,547		41,882		51,547		38,660

Fair Value of Assets And Liabilities Measured on Recurring Basis



	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 agreements	—		—		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

The following table discloses by level within the fair value hierarchy the Company’s assets and liabilities measured and reported on the Consolidated Balance Sheets as of December 31, 2016 at fair value on a recurring basis (dollars in thousands):



	Level 1		Level 2		Level 3		Counterparty and Cash Collateral Netting (1)			Total
December 31, 2016
Assets:
Energy commodity derivatives	$	—	$	47,994	$	—	$	(46,099	)	$	1,895
Level 3 energy commodity derivatives:
Natural gas exchange agreement	—		—		69		(69		)	—
Power exchange agreement	—		—		25		(25		)	—
Foreign currency exchange derivatives	—		5		—		(5		)	—
Interest rate swap derivatives	—		13,098		—		(4,348		)	8,750
Deferred compensation assets:
Mutual Funds:
Fixed income securities (2)	1,789		—		—		—			1,789
Equity securities (2)	5,481		—		—		—			5,481
Total	$	7,270	$	61,097	$	94	$	(50,546	)	$	17,915



	Level 1		Level 2		Level 3		Counterparty and Cash Collateral Netting (1)			Total
Liabilities:
Energy commodity derivatives	$	—	$	56,871	$	—	$	(55,957	)	$	914
Level 3 energy commodity derivatives:
Natural gas exchange agreement	—		—		5,954		(69		)	5,885
Power exchange agreement	—		—		13,474		(25		)	13,449
Power option agreement	—		—		76		—			76
Foreign currency exchange derivatives	—		28		—		(5		)	23
Interest rate swap derivatives	—		73,978		—		(39,248		)	34,730
Total	$	—	$	130,877	$	19,504	$	(95,304	)	$	55,077


(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 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
Year ended December 31, 2017:
Balance as of January 1, 2017	$	(5,885	)	$	(13,449	)	$	(76	)	$	(19,410	)
Total gains or (losses) (realized/unrealized):
Included in regulatory assets/liabilities (1)	3,292			(7,674		)	57			(4,325		)
Settlements	(571		)	7,878			—			7,307
Ending balance as of December 31, 2017 (2)	$	(3,164	)	$	(13,245	)	$	(19	)	$	(16,428	)
Year ended December 31, 2016:
Balance as of January 1, 2016	$	(5,039	)	$	(21,961	)	$	(124	)	$	(27,124	)
Total gains or (losses) (realized/unrealized):
Included in regulatory assets/liabilities (1)	259			400			48			707
Settlements	(1,105		)	8,112			—			7,007
Ending balance as of December 31, 2016 (2)	$	(5,885	)	$	(13,449	)	$	(76	)	$	(19,410	)
Year ended December 31, 2015:
Balance as of January 1, 2015	$	(35	)	$	(23,299	)	$	(424	)	$	(23,758	)
Total gains or (losses) (realized/unrealized):
Included in regulatory assets/liabilities (1)	(6,008		)	(6,198		)	300			(11,906		)
Settlements	1,004			7,536			—			8,540
Ending balance as of December 31, 2015 (2)	$	(5,039	)	$	(21,961	)	$	(124	)	$	(27,124	)


(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.