Stock Based Compensation - Stock Options Transactions (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Option Shares
Outstanding at beginning of period (in shares)	50,985
Acquired in acquisition (in shares)	0
Granted (in shares)	0
Exercised (in shares)	(3,300)	(3,300)
Forfeited (in shares)	0
Expired (in shares)	(1,650)
Outstanding at end of period (in shares)	46,035
Exercisable at end of period (in shares)	46,035
Weighted Average Exercise Price
Outstanding at beginning of period (in dollars per share)	$ 24.09
Acquired in acquisition (in dollars per share)	0.00
Granted (in dollars per share)	0.00
Exercised (in dollars per share)	25.76
Forfeited (in dollars per share)	0.00
Expired (in dollars per share)	33.33
Outstanding at end of period (in dollars per share)	23.64
Exercisable at end of period (in dollars per share)	$ 23.64
Weighted Average Remaining Contractual Term
Outstanding at end of period	7 months 1 day
Exercisable at end of period	7 months 1 day
Aggregate Intrinsic Value
Outstanding at end of period	$ 643
Exercisable at end of period	$ 643