Stock-Based Compensation Plans (Tables)

3 Months Ended

Mar. 31, 2015

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Allocation of Stock-Based Compensation by Functional Category

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

	Three Months Ended March 31,
	2015		2014
Direct operating expense	$	886	$	852
Brokered natural gas and marketing expense		506		528
Exploration expense		732		1,153
General and administrative expense		11,080		11,604
Termination costs		1,287		—
Total	$	14,491	$	14,137

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		(92,934	)		46.38
Expired/forfeited		(9,189	)		65.55
Outstanding at March 31, 2015		1,864,426		$	60.44

Summary of Performance Share Unit Awards Activity

The following is a summary of our non-vested PSU awards outstanding at March 31, 2015:

	Units			Weighted Average Grant Date Fair Value
Outstanding at December 31, 2014		134,341		$	86.11
Units granted (a)		77,119			55.17
Units vested		(26,102	)		76.75
Units forfeited		(2,679	)		82.60
Outstanding at March 31, 2015		182,679		$	74.44

^(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.

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 quarter 2015:

	Three Months Ended March 31, 2015
Risk-free interest rate		1.05	%
Expected annual volatility		33.9	%
Grant date fair value per unit	$	55.17

Restricted Stock and Restricted Stock Units Outstanding

The following is a summary of the status of our non-vested restricted stock outstanding at March 31, 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		548,046			52.45		94,573			52.25
Vested		(127,637	)		69.98		(73,396	)		74.14
Forfeited		(8,957	)		69.99		(9,574	)		72.77
Outstanding at March 31, 2015		771,867		$	62.03		316,107		$	73.60