Share-Based Payments (Details) $ / shares in Units, $ in Thousands				12 Months Ended			50 Months Ended
	Jun. 01, 2017 shares	Jun. 02, 2016 shares	Jun. 04, 2015 director	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Jun. 30, 2016 shares	May 15, 2012 shares
Share-Based Payments
Shares authorized (as a percent)					3.00%
Shares reserved for issuance under the Equity plan (in shares)					1,237,711			308,335
Number of shares remained available for issuance (in shares)					512,262
Stock-based compensation expense recognized | $				$ 981	$ 1,700	$ 2,300
Restricted common stock
Share-Based Payments
Vested (in shares)				152,630	200,983	175,824
Shares of Restricted Stock
Restricted Stock Shares Outstanding, beginning of period				707,861	688,394
Granted (in shares)				17,588	19,467		725,449
Restricted Stock Shares Outstanding, end of period				725,449	707,861	688,394
Unvested at end of year (in shares)				83,155	218,197
Weighted Average Grant Date Fair Value
Outstanding at beginning of period (in dollars per share) | $ / shares				$ 17.17	$ 17.39
Granted (in dollars per share) | $ / shares				10.30	9.40
Outstanding at end of year (in dollars per share) | $ / shares				17.00	17.17	$ 17.39
Unvested at end of year (in dollars per share) | $ / shares				$ 14.07	$ 14.98
Restricted common stock | Director Deferred Fee Plan
Shares of Restricted Stock
Granted (in shares)				2,052	2,335
Restricted common stock | March 2017
Shares of Restricted Stock
Unvested at end of year (in shares)				0	133,334
Restricted common stock | June 2017
Shares of Restricted Stock
Unvested at end of year (in shares)				0	18,196
Restricted common stock | March 2018
Shares of Restricted Stock
Unvested at end of year (in shares)				66,667	66,667
Restricted common stock | June 2018
Shares of Restricted Stock
Unvested at end of year (in shares)				16,488	0
Restricted common stock | Director
Share-Based Payments
Awards granted to each of the entity's independent directors (in shares)	3,884	4,283
Number of independent directors to whom awards were granted | director			4
Shares of Restricted Stock
Granted (in shares)	15,536	17,132
Equity awards
Share-Based Payments
Unamortized compensation expense | $				$ 66	$ 67
Liability awards
Share-Based Payments
Unamortized compensation expense | $				$ 111	$ 895