Stock-Based Compensation Plans (Tables)

9 Months Ended

Sep. 30, 2015

Allocation of Stock-Based Compensation by Functional Category

The following table details the allocation of stock-based compensation to functional expense categories (in thousands):

		Three Months Ended September 30,					Nine Months Ended September 30,
		2015			2014		2015		2014
Direct operating expense	$	609		$	720	$	2,149	$	3,509
Brokered natural gas and marketing expense		618			656		1,743		2,314
Exploration expense		688			1,033		2,171		3,408
General and administrative expense		11,512			11,556		38,545		43,856
Termination costs		(1	)		—		1,720		—
Total stock-based compensation	$	13,426		$	13,965	$	46,328	$	53,087

Stock Option and SARs Activities

Information with respect to SARs activity is summarized below:

	Shares			Weighted Average Exercise Price
Outstanding at December 31, 2014		1,966,549		$	59.80
Exercised		(427,598	)		45.67
Expired/forfeited		(9,469	)		65.04
Outstanding at September 30, 2015		1,529,482		$	63.71

Summary of Performance Share Unit Awards Activity

The following is a summary of our non-vested PSU awards outstanding at September 30, 2015:

	Units			Weighted Average Grant Date Fair Value
Outstanding at December 31, 2014		134,341		$	86.11
Units granted (a)		276,204			56.78
Units vested		(103,397	)		69.67
Units forfeited		(2,679	)		82.60
Outstanding at September 30, 2015		304,469		$	65.12

^(a) Amounts granted reflect the number of performance units granted; however, the actual payout of shares will be between zero percent and 150% of the performance units granted depending on the total shareholder return ranking compared to the peer companies at the end of the three-year performance period.

Restricted Stock and Restricted Stock Units Outstanding

The following is a summary of the status of our non-vested restricted stock outstanding at September 30, 2015:

	Equity Awards					Liability Awards
	Shares			Weighted Average Grant Date Fair Value		Shares			Weighted Average Grant Date Fair Value
Outstanding at December 31, 2014		360,415		$	79.60		304,504		$	80.33
Granted		586,311			52.35		342,495			56.01
Vested		(338,327	)		66.30		(260,622	)		68.39
Forfeited		(28,994	)		64.88		(8,294	)		74.22
Outstanding at September 30, 2015		579,405		$	60.53		378,083		$	66.67

Performance Shares

Schedule of Share Based Payment Award Performance Stock Awards Valuation Assumptions

The following assumptions were used to estimate the fair value of PSUs granted during first nine months 2015 and 2014:

	Nine Months Ended September 30,
	2015			2014
Risk-free interest rate		1.0	%		0.77	%
Expected annual volatility		33	%		33	%
Weighted average grant date fair value per unit	$	56.78		$	86.14