Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2015

Schedule of Finite-Lived Intangible Assets

The following table summarizes the carrying values of our intangible assets as of December 31, 2015 and 2014:



In thousands	Helium Production Rights			CO₂ Purchase Contract			Total
December 31, 2015
Intangible asset value	$	55,266		$	34,341		$	89,607
Accumulated amortization	(15		)	(5,915		)	(5,930		)
Net book value as of December 31, 2015	$	55,251		$	28,426		$	83,677

December 31, 2014
Intangible asset value	$	55,266		$	34,341		$	89,607
Accumulated amortization	(15		)	(3,625		)	(3,640		)
Net book value as of December 31, 2014	$	55,251		$	30,716		$	85,967

Schedule of Finite-Lived Intangible Assets, Future Amortization Expense

As of December 31, 2015, our estimated amortization expense for our intangible assets subject to amortization over the next five years is as follows:



In thousands
2016	$	2,289
2017	2,488
2018	2,788
2019	2,858
2020	2,834

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 (loss) per common share calculations for the periods indicated:



	Year Ended December 31,
In thousands	2015	2014	2013
Basic weighted average common shares outstanding	348,802	348,962	366,659
Potentially dilutive securities
Restricted stock, stock options, SARs and performance-based equity awards	—	2,205	3,218
Diluted weighted average common shares outstanding	348,802	351,167	369,877

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

The following securities could potentially dilute earnings per share in the future, but were excluded from the computation of diluted net income (loss) per share, as their effect would have been antidilutive:



	Year Ended December 31,
In thousands	2015	2014	2013
Stock options and SARs	9,619	4,775	3,598
Restricted stock and performance-based equity awards	3,867	417	365