Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2018

Fair Value Disclosures [Abstract]

Valuation of Financial Instruments by Pricing Levels

The following tables summarize the valuation of financial instruments by pricing levels that were accounted for at fair value on a recurring basis as of March 31, 2018 and December 31, 2017.

	Fair value measurements at March 31, 2018 using:
In thousands	Level 1		Level 2		Level 3		Total
Derivative assets:
Swaps	$	—	$	8,581	$	—	$	8,581
Total	$	—	$	8,581	$	—	$	8,581
	Fair value measurements at December 31, 2017 using:
In thousands	Level 1		Level 2		Level 3		Total
Derivative assets:
Swaps	$	—	$	2,603	$	—	$	2,603
Total	$	—	$	2,603	$	—	$	2,603

Quantitative Information about Significant Unobservable Inputs

The following table sets forth quantitative information about the significant unobservable inputs used by the Company to calculate the fair value of proved crude oil and natural gas properties using a discounted cash flow method.

Unobservable Input	Assumption
Future production	Future production estimates for each property
Forward commodity prices	Forward NYMEX strip prices through 2022 (adjusted for differentials), escalating 3% per year thereafter
Operating costs	Estimated costs for the current year, escalating 3% per year thereafter
Productive life of field	Ranging from 1 to 38 years
Discount rate	10%

Property Impairments

The following table sets forth the non-cash impairments of both proved and unproved properties for the indicated periods. Proved and unproved property impairments are recorded under the caption “Property impairments” in the unaudited condensed consolidated statements of comprehensive income.

	Three months ended March 31,
In thousands	2018		2017
Proved property impairments	$	—	$	871
Unproved property impairments	33,784		50,501
Total	$	33,784	$	51,372

Fair Values of Financial Instruments not Recorded at Fair Value

The following table sets forth the estimated fair values of financial instruments that are not recorded at fair value in the condensed consolidated financial statements.

	March 31, 2018				December 31, 2017
In thousands	Carrying Amount		Estimated Fair Value		Carrying Amount		Estimated Fair Value
Debt:
Revolving credit facility	$	—	$	—	$	188,000	$	188,000
Note payable	9,411		9,300		9,974		9,900
5% Senior Notes due 2022	1,997,678		2,032,500		1,997,576		2,040,000
4.5% Senior Notes due 2023	1,487,240		1,517,800		1,486,690		1,526,800
3.8% Senior Notes due 2024	992,311		964,200		992,036		988,800
4.375% Senior Notes due 2028	988,045		976,200		988,061		987,200
4.9% Senior Notes due 2044	691,394		668,900		691,354		679,900
Total debt	$	6,166,079	$	6,168,900	$	6,353,691	$	6,420,600