Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2013

The following table summarizes the changes in goodwill for the years ended December 31, 2013 and 2012:



	Year Ended December 31,
In thousands	2013		2012
Beginning of year balance	$	1,283,590	$	1,236,318
Goodwill related to the Thompson Field acquisition	—		47,272
End of year balance	$	1,283,590	$	1,283,590

Schedule of Finite-Lived Intangible Assets

The following table summarizes the intangible asset value and related accumulated amortization as of December 31, 2013 and 2012:



In thousands	Helium Production Rights		CO₂ Purchase Contract			Total
December 31, 2013
Intangible asset value	$	55,266	$	33,931		$	89,197
Accumulated amortization	—		(1,319		)	(1,319		)
Net book value as of December 31, 2013	$	55,266	$	32,612		$	87,878

December 31, 2012
Intangible asset value	$	55,266	$	33,901		$	89,167
Accumulated amortization	—		—			—
Net book value as of December 31, 2012	$	55,266	$	33,901		$	89,167

Schedule of Finite-Lived Intangible Assets, Future Amortization Expense

At December 31, 2013, our estimated amortization expense for our intangible assets subject to amortization over the next five years is as follows:



In thousands
2014	$	2,748
2015	2,843
2016	2,915
2017	2,915
2018	3,568

Weighted average shares used in basic and diluted net income per common share

The following is a reconciliation of the weighted average shares used in the basic and diluted net income per common share calculations for the periods indicated:



	Year Ended December 31,
In thousands	2013	2012	2011
Basic weighted average common shares	366,659	385,205	396,023
Potentially dilutive securities:
Restricted stock, stock options, SARs and performance-based equity awards	3,218	3,733	4,935
Diluted weighted average common shares	369,877	388,938	400,958