Shareholders' Equity Rollforward (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
As of beginning balance		$ 221,639
Net income (loss)		10,295	$ 28,081
All Other Changes		(1,670)
As of ending balance		230,264
Share-based compensation		1,576	$ 846
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		2,700
Common stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
As of beginning balance		150
All Other Changes	[1]	1
As of ending balance		151
Paid-in capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
As of beginning balance		194,123
All Other Changes	[1]	988
As of ending balance		195,111
Retained earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
As of beginning balance		27,366
Net income (loss)		10,295
All Other Changes	[1]	(2,659)
As of ending balance		35,002
Accumulated other comprehensive income
Increase (Decrease) in Stockholders' Equity [Roll Forward]
As of beginning balance		0
As of ending balance		$ 0
Time Vested Restricted Stock Units [Domain]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares, Issued		37,845
Performance Restricted Stock Units [Domain]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares, Issued		1,495

[1] Includes equity-classified share-based compensation of $1.6 million during the three months ended March 31, 2018. During the three months ended March 31, 2018, 37,845 and 1,495 shares of common stock were issued in connection with the vesting of certain time-vested restricted stock units (“RSUs”) and performance restricted stock units (“PRSUs”), net of shares withheld for income taxes, respectively. Also includes a write-off of $2.7 million for certain accounts receivable attributable to natural gas imbalances accounted for under the entitlements method prior to January 1, 2018 in accordance with the adoption of ASC Topic 606 (see Note 5).