Compensation Plans (Tables)

9 Months Ended

Sep. 30, 2012

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Nonvested Restricted Stock Units Activity [Table Text Block]

A summary of the status and activity of non-vested RSUs for the nine-month period ended September 30, 2012, is presented in the following table:



	RSUs		Weighted-Average Grant-Date Fair Value
Non-vested, at beginning of year	308,877		$	44.33
Granted	369,332		$	49.32
Vested	(160,991	)	$	32.02
Forfeited	(22,305	)	$	51.06
Non-vested, at end of quarter	494,913		$	51.75

Schedule of Nonvested Performance-based Units Activity [Table Text Block]

A summary of the status and activity of non-vested PSUs for the nine-month period ended September 30, 2012, is presented in the following table:



	PSUs⁽¹⁾		Weighted-Average Grant-Date Fair Value
Non-vested, at beginning of year	885,894		$	57.52
Granted	314,853		$	51.98
Vested	(473,750	)	$	43.96
Forfeited	(34,708	)	$	65.22
Non-vested, at end of quarter	692,289		$	63.90

Schedule of stock option grants under prior stock option plans

A summary of activity associated with the Company’s Stock Option Plan for the nine months ended September 30, 2012, is presented in the following table:



	Shares		Weighted- Average Exercise Price		Aggregate Intrinsic Value (in thousands)
Outstanding, at beginning of year	508,214		$	13.86	$	30,109
Exercised	(151,083	)	$	12.39	$	8,308
Forfeited	—		$	—
Outstanding, at end of quarter	357,131		$	14.48	$	14,155
Vested and exercisable, at end of quarter	357,131		$	14.48	$	14,155

Summary of cash payments made or accrued under the Net Profits Plan

Cash payments made or accrued under the Company’s Net Profits Interest Bonus Plan (“Net Profits Plan”) that have been recorded as either general and administrative expense or exploration expense are presented in the table below:



	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
	2012		2011		2012		2011
	(in thousands)
General and administrative expense	$	4,083	$	4,229	$	12,177	$	14,820
Exploration expense	403		507		1,421		1,569
Total	$	4,486	$	4,736	$	13,598	$	16,389