Derivative Instruments (Tables)

6 Months Ended

Jun. 30, 2019

Derivative Instruments

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

	Natural GasSwaps
	(MMBTUs)
Year	(in millions)
2019	14.2
2020	23.9
2021	21.7
2022	15.0
2023	9.9
2024	4.7
Total	89.4

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

The table below reflects the fair value of derivative instruments and their effect on our consolidated balance sheets at June 30, 2019 and December 31, 2018.

	Balance Sheet Location	Fair Value
		2019		2018
		(dollars in thousands)
Assets:
Natural gas swaps	Other current assets	$	—	$	226
Liabilities:
Natural gas swaps	Other current liabilities	$	10,709	$	2,066
Natural gas swaps	Other deferred credits	$	12,291	$	11,314

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

	Statement of
	Revenues and
	Expenses	Three months ended June 30,				Six months ended June 30,
	Location	2019		2018		2019		2018
		(dollars in thousands)
Natural Gas Swaps gains	Fuel	$	11	$	359	$	224	$	1,751
Natural Gas Swaps losses	Fuel		(1,126)		(111)		(1,799)		(859)
Total		$	(1,115)	$	248	$	(1,575)	$	892

Schedule of unrealized losses on derivative instruments deferred on the balance sheet

The following table presents the unrealized losses on derivative instruments deferred on the balance sheet at June 30, 2019 and December 31, 2018.

	Balance Sheet
	Location	2019		2018
		(dollars in thousands)
Natural gas swaps	Regulatory asset	$	23,000	$	13,154
Total		$	23,000	$	13,154