Derivative Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2018

Derivative Instruments And Hedging Activities Disclosure [Abstract]

Summary of Open Commodity Derivative Contracts

Year	Index	Total Volumes		Weighted Average Price per Unit			Fair Value - September 30, 2018
		(in millions)					Asset (Liability)
Natural gas fixed price swaps		(Mmbtu)		($/Mmbtu)
2018 (October through December)	NYMEX-Henry Hub		60.5	$	2.88		$	(9,536	)
2019	NYMEX-Henry Hub		163.9	$	2.82			(188	)
2020	NYMEX-Henry Hub		15.5	$	2.76			(1,673	)
Natural gas basis swaps (1)		(Mmbtu)		($/Mmbtu)
2018 (October through December)	NW Rockies Basis Swap		51.5	$	(0.66	)	$	(4,170	)
2019	NW Rockies Basis Swap		84.5	$	(0.70	)		(10,523	)
2020	NW Rockies Basis Swap		—	$	—			—
Crude oil fixed price swaps		(Bbl)		($/Bbl)
2018 (October through December)	NYMEX-WTI		0.6	$	60.45		$	(7,472	)
2019	NYMEX-WTI		1.7	$	58.83			(21,295	)
2020	NYMEX-WTI		0.1	$	60.05			(734	)

⁽¹⁾ Represents swap contracts that fix the basis differentials for gas sold at or near Opal, Wyoming and the value of natural gas established on the last trading day of the month by the NYMEX for natural gas swaps for the respective period.

Subsequent to September 30, 2018 and through October 25, 2018, the Company entered into the following open commodity derivative contracts to manage commodity price risk.

Type	Index	Remaining Contract Period	Volume/MMBTU/Day		Weighted Average Floor Price ($/MMBTU)	Weighted Average Ceiling Price ($/MMBTU)
Collars
	NYMEX	January - March 2020		100,000	2.75	3.18

Summary of Pre-tax Realized and Unrealized Gain (Loss) Recognized Related to Derivative Instruments

	For the Three Months						For the Nine Months
	Ended September 30,						Ended September 30,
Commodity Derivatives:	2018			2017			2018			2017
Realized gain (loss) on commodity derivatives - natural gas	$	(5,468	)	$	8,884		$	6,958		$	8,016
Realized loss on commodity derivatives - oil		(5,318	)		—			(10,008	)		—
Unrealized gain (loss) on commodity derivatives		(11,018	)		(4,234	)		(72,557	)		4,133
Total gain (loss) on commodity derivatives	$	(21,804	)	$	4,650		$	(75,607	)	$	12,149