Stockholders' Equity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Proceeds from issuance of common stock	$ 1,061,000	$ 87,267,000	$ 30,920,000
Payments of Stock Issuance Costs	$ 0	$ 5,469,000	1,143,000
Equity Offering [Member]
Class of Stock [Line Items]
Shares available for sale	6,382,978
Underwriter Option to Purchase Shares	957,446
Payments of Stock Issuance Costs	$ 5,520,000
Underwriting Fees	5,175,000
Fees and Commissions	$ 345,000
Equity Offering [Member] | Common Stock [Member]
Class of Stock [Line Items]
Shares Issued, Price Per Share	$ 11.75
Stock Issued During Period, Shares, New Issues	7,340,424
Proceeds from issuance of common stock	$ 86,250,000
ATM Offering [Member]
Class of Stock [Line Items]
Commission Percentage		3.00%
Maximum ATM Offering		$ 30,000,000
Payments of Stock Issuance Costs		1,143,000
Underwriting Fees		900,000
Fees and Commissions		$ 243,000
ATM Offering [Member] | Common Stock [Member]
Class of Stock [Line Items]
Shares Issued, Price Per Share		$ 9.04
Stock Issued During Period, Shares, New Issues		3,300,000
Proceeds from issuance of common stock		$ 30,000,000
Restricted Stock Awards | 2010 Equity Incentive Plan
Class of Stock [Line Items]
Equity Instruments Other than Options, Vested in Period, Fair Value	$ 645,000		$ 2,433,000