Stock Compensation Plans (Tables)

12 Months Ended

Dec. 31, 2013

Stock Compensation Plans [Line Items]

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs

Stock-based compensation costs for the years ended December 31, 2013, 2012 and 2011, are as follows:

	Year Ended December 31,
In thousands	2013		2012		2011
Stock-based compensation expensed:
General and administrative expenses	$	30,429	$	26,463	$	30,256
Lease operating expenses	2,574		2,847		2,621
Other expenses	—		—		313
Total stock-based compensation expensed	33,003		29,310		33,190
Stock-based compensation capitalized	9,088		8,587		6,998
Total cost of stock-based compensation arrangements	$	42,091	$	37,897	$	40,188
Income tax benefit recognized for stock-based compensation arrangements	$	12,541	$	11,284	$	12,612

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions

	2013			2012			2011
Weighted average fair value of SARs granted	$	6.72		$	8.90		$	9.68
Risk-free interest rate	0.67		%	0.79		%	1.74		%
Expected life	3.6 to 4.8 years			4.0 to 5.0 years			4.0 to 5.0 years
Expected volatility	50.4		%	64.9		%	63.3		%
Dividend yield	—		%	—		%	—		%

Summary of stock option and SARs activity

The following is a summary of our stock option and SAR activity:

	Number of Awards		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2012	10,445,135		$	14.75
Granted	720,859		16.95
Exercised	(1,970,426	)	9.33
Forfeited	(113,509	)	17.31
Expired	(95,144	)	22.74
Outstanding at December 31, 2013	8,986,915		16.00		3.3	$	19,319
Exercisable at end of period	6,632,141		$	15.51	2.7	$	18,970

Disclosure of intrinsic value of stock options exercised and grant-date fair value of awards vested

The following is a summary of the total intrinsic value of stock options and SARs exercised and grant-date fair value of stock options and SARs vested:

	Year Ended December 31,
In thousands	2013		2012		2011
Intrinsic value of stock options exercised	$	17,287	$	17,315	$	20,463
Grant-date fair value of stock options and SARs vested	12,852		26,391		11,416

Schedule of Cash Proceeds Received from Share-based Payment Awards

The following is a summary of cash received from stock option exercises under share-based payment arrangements and tax benefits realized from the exercises of stock options and SARs:

	Year Ended December 31,
In thousands	2013		2012		2011
Cash received from stock option exercises	$	5,487	$	6,022	$	4,685
Tax benefit realized for the exercises of stock options and SARs	437		458		539

Performance equity awards [Member]

Stock Compensation Plans [Line Items]

Schedule of Nonvested Performance-based Units Activity

A summary of the status of the nonvested performance-based equity awards (presented at the target level) during the year ended December 31, 2013 is as follows:

	Performance-Based Operational Awards				Performance-Based TSR Awards
	Number of Awards		Weighted Average Grant-Date Fair Value		Number of Awards	Weighted Average Grant-Date Fair Value
Nonvested at December 31, 2012	100,193		$	17.27	86,917	$	24.68
Granted	215,258		16.77		209,474	20.08
Vested (1)	(100,193	)	17.27		—	—
Forfeited	(5,784	)	16.77		—	—
Nonvested at December 31, 2013	209,474		16.77		296,391	21.43

(1) During 2013, the 2012 annual Performance-based Operational Awards vested, and award holders received shares equivalent to 136% of the number of target-level shares.

Performance-based TSR Awards [Member]

Stock Compensation Plans [Line Items]

Summary of Share-Based Award Valuation Assumptions

The range of assumptions used in the Monte Carlo simulation valuation approach for Performance-based TSR Awards, which were granted for the first time during 2012, are as follows:

	Year Ended December 31,
	2013			2012
Weighted average fair value of Performance-based TSR Award granted	$	20.08		$	24.68
Risk-free interest rate	0.41		%	0.42		%
Expected life	3.0 years			2.8 years
Expected volatility	42.3		%	45.2		%
Dividend yield	—		%	—		%

Performance-based Operational Award [Member]

Stock Compensation Plans [Line Items]

Summary of Vesting Date Fair Value Of Awards

The following is a summary of the total vesting date fair value of performance-based equity awards:

	Year Ended December 31,
In thousands	2013		2012		2011
Vesting date fair value of Performance-based Operational Awards	$	2,541	$	2,191	$	10,892

2004 Omnibus Stock and Incentive Plan | Restricted Stock [Member]

Stock Compensation Plans [Line Items]

Summary of Vesting Date Fair Value Of Awards

The following is a summary of the total vesting date fair value of restricted stock under the 2004 Plan:

	Year Ended December 31,
In thousands	2013		2012		2011
Fair value of restricted stock vested	$	21,529	$	22,332	$	12,355

Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity

A summary of the status of our nonvested restricted stock grants issued under our 2004 Plan and the changes during the year ended December 31, 2013 is presented below:

	Number of Shares		Weighted Average Grant-Date Fair Value
Nonvested at December 31, 2012	3,406,207		$	15.60
Granted	1,805,467		16.96
Vested	(1,310,347	)	16.21
Forfeited	(165,917	)	17.23
Nonvested at December 31, 2013	3,735,410		15.97

Encore Plan [Member] | Restricted Stock [Member]

Stock Compensation Plans [Line Items]

Summary of Vesting Date Fair Value Of Awards

The following is a summary of the total vesting date fair value of restricted stock under the Encore Plan:

	Year Ended December 31,
In thousands	2013		2012		2011
Fair value of restricted stock vested	$	512	$	584	$	2,259

Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity

A summary of the status of the non-vested restricted stock grants under the Encore Plan and the changes during the year ended December 31, 2013 is presented below:

	Number of Shares		Weighted Average Grant-Date Fair Value
Nonvested at December 31, 2012	56,258		$	15.43
Vested	(31,140	)	15.43
Forfeited	(3,377	)	15.43
Nonvested at December 31, 2013	21,741		15.43