Stockholders' Equity (Details) $ / shares in Units, $ in Thousands		12 Months Ended
	Aug. 16, 2016 USD ($) $ / shares shares	Dec. 31, 2017 item shares	Dec. 31, 2016 USD ($)
Equity offerings
Shares of common stock sold	7,043,750
Price per share of common stock sold (in dollars per share) | $ / shares	$ 12.35
Proceeds from equity offering | $	$ 82,900		$ 83,511
2002 Stock Incentive Plan
Equity-Based Compensation
Maximum number of shares provided for grant under equity-based incentive compensation plan		2,000,000
Number of vesting requirements | item		0
Number of shares available for grant under the plan		1,944,428
Underwriter Overallotment Option
Equity offerings
Shares of common stock sold	918,750