Derivative Instruments (Tables)

12 Months Ended

Dec. 31, 2017

Derivative [Line Items]

Summary of Outstanding Contracts with Respect to Natural Gas

Period and Type of Contract	MMBtus	Swaps Weighted Average Price
January 2018 - March 2018
Swaps - Henry Hub	6,300,000	$	3.28

Realized and Unrealized Gains and Losses on Derivative Instruments

Cash receipts in the following table reflect gains on diesel fuel derivatives which matured during the period, calculated as the difference between the contract price and the market settlement price of matured contracts. Non-cash gains and losses below represent the change in fair value of diesel fuel derivatives held at period end, if any, and the reversal of previously recognized non-cash gains or losses on derivative contracts that matured during the period.

	Year ended December 31,
In thousands	2017			2016
Cash received on diesel fuel derivatives	$	2,845		$	699
Non-cash gain (loss) on diesel fuel derivatives	(4,060		)	4,060
Gain (loss) on diesel fuel derivatives, net	$	(1,215	)	$	4,759

	Year ended December 31,
In thousands	2017			2016			2015
Cash received (paid) on derivatives:
Natural gas fixed price swaps	$	40,095		$	88,823		$	39,670
Natural gas collars	(10,539		)	—			29,883
Cash received on derivatives, net	29,556			88,823			69,553
Non-cash gain (loss) on derivatives:
Crude oil written call options	—			38			4,715
Natural gas fixed price swaps	18,960			(120,784		)	41,828
Natural gas collars	43,131			(39,936		)	(25,011		)
Non-cash gain (loss) on derivatives, net	62,091			(160,682		)	21,532
Gain (loss) on crude oil and natural gas derivatives, net	$	91,647		$	(71,859	)	$	91,085

Balance sheet offsetting of derivative assets and liabilities

The following table presents the gross amounts of recognized crude oil, natural gas, and diesel fuel derivative assets and liabilities, as applicable, the amounts offset under netting arrangements with counterparties, and the resulting net amounts presented in the consolidated balance sheets for the periods presented, all at fair value.

	December 31,
In thousands	2017		2016
Commodity derivative assets:
Gross amounts of recognized assets	$	2,603	$	4,061
Gross amounts offset on balance sheet	—		—
Net amounts of assets on balance sheet	2,603		4,061
Commodity derivative liabilities:
Gross amounts of recognized liabilities	—		(59,489		)
Gross amounts offset on balance sheet	—		—
Net amounts of liabilities on balance sheet	$	—	$	(59,489	)

Schedule Of Derivative Assets Liabilities At Fair Value Net By Balance Sheet Classification Table

The following table reconciles the net amounts disclosed above to the individual financial statement line items in the consolidated balance sheets.

	December 31,
In thousands	2017		2016
Derivative assets	$	2,603	$	4,061
Noncurrent derivative assets	—		—
Net amounts of assets on balance sheet	2,603		4,061
Derivative liabilities	—		(59,489		)
Noncurrent derivative liabilities	—		—
Net amounts of liabilities on balance sheet	—		(59,489		)
Total derivative assets (liabilities), net	$	2,603	$	(55,428	)