Stock-Based Compensation - Assumptions and Activity (Details) - USD ($)	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Weighted Average Exercise Price
Aggregate intrinsic value of all options outstanding	$ 1,400
Aggregate intrinsic value of all options exercisable	$ 100
Stock Options.
Assumptions used to determine fair value of stock options granted
Dividend yield (as a percent)	0.00%	0.00%
Expected volatility (as a percent)	40.00%	41.30%
Expected life of option	5 years	5 years
Risk-free interest rate (as a percent)	2.80%	1.80%
Fair value of each option on grant date (in dollars per share)	$ 3.38	$ 3.43
Shares
Outstanding at beginning of period (in shares)	18,168
Granted (in shares)	2,750	2,250
Exercised (in shares)	0	(250)
Expired and forfeited (in shares)	(2,918)
Outstanding at end of period (in shares)	18,000
Exercisable at end of period (in shares)	12,247
Weighted Average Exercise Price
Outstanding at beginning of period (in dollars per shares)	$ 13.81
Granted (in dollars per share)	8.63
Expired and forfeited (in dollars per share)	12.56
Outstanding at end of period (in dollars per share)	13.22
Exercisable at end of period (in dollars per share)	$ 15.09