Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2016

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, 2016, and the year in which the costs were incurred follows:

	December 31, 2016
	Costs Incurred During:
In thousands	2016		2015		2014		2013 and Prior		Total
Property acquisition costs	$	7,528	$	—	$	4,875	$	592,184	$	604,587
Exploration and development	21,119		24,812		95,397		70,156		211,484
Capitalized interest	25,220		28,302		21,179		37,047		111,748
Total	$	53,867	$	53,114	$	121,451	$	699,387	$	927,819