Stock Compensation Plans - Time-Based Restricted Stock Activity (Details) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Compensation expense
Total Compensation	$ 5,372	$ 4,871	$ 5,650
Restricted Stock, subject to time-based criteria
Compensation expense
Total Compensation	2,148	$ 2,177	$ 1,356
Unamortized future compensation expense	$ 2,734
Summary of restricted stock activity
Outstanding shares	276
Shares vested	(110)
Shares awarded	120
Shares forfeited	(18)
Outstanding shares	269	276
Weighted average remaining term (years)
Outstanding (years)	1 year 6 months 29 days	1 year 11 months 12 days
Aggregate intrinsic value
Outstanding, beginning balance (in dollars)	$ 3,767
Shares vested (in dollars)	1,513
Shares awarded (in dollars)	1,717
Shares forfeited (in dollars)	337
Outstanding, Ending balance (in dollars)	$ 3,736	$ 3,767
Executive Officer | Restricted Stock, subject to time-based criteria
Plan information
Vesting period (in years)		4 years