Unevaluated Property (Tables)

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment [Abstract]

Summary of unevaluated properties excluded from oil and natural gas properties being amortized

A summary of the unevaluated property costs excluded from oil and natural gas properties being amortized at December 31, 2018, and the year in which the costs were incurred follows:

	December 31, 2018
	Costs Incurred During:
In thousands	2018		2017		2016		2015 and Prior		Total
Property acquisition costs	$	—	$	8,527	$	—	$	582,364	$	590,891
Exploration and development	9,849		6,948		20,673		189,890		227,360
Capitalized interest	36,510		30,762		25,220		85,957		178,449
Total	$	46,359	$	46,237	$	45,893	$	858,211	$	996,700