Shareholders' Equity Rollforward (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2017 USD ($)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
As of beginning balance	$ 185,548
Net income (loss)	49,410
All Other Changes	1,738
As of ending balance	236,696
Share-based compensation	1,700
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	1,738	[1]
As of ending balance	192,359
Retained earnings (accumulated deficit)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
As of beginning balance	(5,296)
Net income (loss)	49,410
As of ending balance	44,114
Accumulated other comprehensive income
Increase (Decrease) in Stockholders' Equity [Roll Forward]
As of beginning balance	73
As of ending balance	$ 73

[1] Includes equity-classified share-based compensation of $1.7 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