Derivative Instruments (Tables)

9 Months Ended

Sep. 30, 2017

Derivative Instruments

Schedule of volume activity of natural gas derivatives that is expected to settle or mature each year

The following table reflects the volume activity of our natural gas derivatives as of September 30, 2017 that is expected to settle or mature each year:

Year	Natural Gas Swaps (MMBTUs) (in millions)
2017	3.8
2018	24.6
2019	18.7
2020	15.9
2021	12.9
2022	5.8
Total	81.7

Schedule of fair value of derivative instruments and effect on our consolidated balance sheets

	Balance Sheet Location		Fair Value
			2017		2016
			(dollars in thousands)
Not designated as hedges:
Assets:
Natural gas swaps	Other current assets	$	3,302	$	13,833
Natural gas swaps	Other deferred charges	$	—	$	3,289
Liabilities:
Natural gas swaps	Other current liabilities	$	—	$	54
Natural gas swaps	Other deferred credits	$	4,109	$	1,977

Schedule of the gross realized gains and (losses) on derivative instruments recognized in margin

	Statement of Revenues and Expenses Location		Three months ended September 30,						Nine months ended September 30,
			2017			2016			2017			2016
			(dollars in thousands)
Not Designated as hedges:
Natural Gas Swaps	Fuel	$	778		$	2,039		$	3,514		$	2,057
Natural Gas Swaps	Fuel		(678	)		(5,923	)		(1,495	)		(18,262	)
		$	100		$	(3,884	)	$	2,019		$	(16,205	)

Schedule of unrealized gains and (losses) on derivative instruments deferred on the balance sheet

	Balance Sheet Location		2017			2016
			(dollars in thousands)
Not designated as hedges:
Natural gas swaps	Regulatory asset	$	(2,788	)	$	(62	)
Natural gas swaps	Regulatory liability		1,981			15,152
Interest rate options	Regulatory asset		—			(5,788	)
Total not designated as hedges		$	(807	)	$	9,302