Shareholders' Equity Rollforward (Details) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
As of beginning balance		$ 185,548
Net income (loss)		43,463
All Other Changes		2,751
As of ending balance		231,762
Share-based compensation		2,700
Proceeds Attributable to Rights Offering		100
Common stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
As of beginning balance		150
As of ending balance		150
Paid-in capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
As of beginning balance		190,621
All Other Changes	[1]	2,751
As of ending balance		193,372
Retained earnings (accumulated deficit)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
As of beginning balance		(5,296)
Net income (loss)		43,463
As of ending balance		38,167
Accumulated other comprehensive income
Increase (Decrease) in Stockholders' Equity [Roll Forward]
As of beginning balance		73
As of ending balance		$ 73
Time Vested Restricted Stock Units [Domain]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares, Issued		12,252

[1] Includes equity-classified share-based compensation of $2.7 million and $0.1 million from the receipt in May 2017 of proceeds attributable to the rights offering in 2016 that had been held in escrow, net of costs to register our common stock