Stock-based Compensation Plans (Tables)

6 Months Ended

Jun. 30, 2021

Allocation of Stock-Based Compensation by Functional Category

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

	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
Direct operating expense	$	340	$	434	$	667	$	884
Brokered natural gas and marketing expense		443		168		893		581
Exploration expense		362		372		748		702
General and administrative expense		9,382		9,179		18,787		17,208
Total stock-based compensation expense	$	10,527	$	10,153	$	21,095	$	19,375

Restricted Stock and Restricted Stock Units Outstanding

The following is a summary of the status of our non-vested restricted stock outstanding at June 30, 2021:

	Restricted Stock Equity Awards					Restricted Stock Liability Awards
	Shares			Weighted Average Grant Date Fair Value		Shares			Weighted Average Grant Date Fair Value
Outstanding at December 31, 2020		2,815,860		$	4.97		1,186,636		$	4.18
Granted		2,340,114			10.20		1,283,039			9.50
Vested		(1,217,427	)		7.45		(941,832	)		6.52
Forfeited		(60,377	)		6.22		—			—
Outstanding at June 30, 2021		3,878,170		$	7.33		1,527,843		$	7.20

Schedule of Share Based Payment Award Performance Stock Awards Valuation Assumptions

The following assumptions were used to estimate the fair value of TSR-PSUs granted during first six months 2021 and 2020:

	Six Months Ended June 30,
	2021			2020
Risk-free interest rate		0.2	%		1.4	%
Expected annual volatility		75	%		65	%
Grant date fair value per unit	$	12.58		$	3.85

Performance-based Internal Performance Awards

Summary of Non-Vested Awards Activities

The following is a summary of our non-vested internal performance awards outstanding at June 30, 2021:

	Number of Units			Weighted Average Grant Date Fair Value
Outstanding at December 31, 2020		1,099,102		$	5.92
Units granted (a)		303,231			9.81
Vested and issued (b)		(306,978	)		12.20
Forfeited		—			—
Outstanding at June 30, 2021		1,095,355		$	7.80

Performance Based TSR - PSUs

Summary of Non-Vested Awards Activities

The following is a summary of our non-vested TSR-PSUs award activities:

	Number of Units			Weighted Average Grant Date Fair Value
Outstanding at December 31, 2020		1,249,524		$	9.55
Units granted (a)		223,687			12.58
Vested and issued (b)		(325,217	)		18.51
Forfeited		—			—
Outstanding at June 30, 2021		1,147,994		$	7.60

(a ) These amounts reflect the number of performance units granted. The actual payout of shares may be between zero and 200% of the performance units granted depending on the total shareholder return ranking compared to our peer companies at the vesting date.

(b) Includes TSR-PSUs awards issued related to the 2018 performance period where the return on our common stock was was negative and therefore, the performance multiple and actual payout was reduced to 100%.