Stock Based Compensation - Stock Options Transactions (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Option Shares
Outstanding at beginning of period (in shares)	58,411
Acquired in acquisition (in shares)	0
Granted (in shares)	0
Exercised (in shares)	(3,300)	(4,134)
Forfeited (in shares)	(578)
Expired (in shares)	(1,320)
Outstanding at end of period (in shares)	53,213
Exercisable at end of period (in shares)	53,213
Weighted Average Exercise Price
Outstanding at beginning of period (in dollars per share)	$ 24.37
Acquired in acquisition (in dollars per share)	0.00
Granted (in dollars per share)	0.00
Exercised (in dollars per share)	21.97
Forfeited (in dollars per share)	23.33
Expired (in dollars per share)	41.67
Outstanding at end of period (in dollars per share)	24.10
Exercisable at end of period (in dollars per share)	$ 24.10
Weighted Average Remaining Contractual Term
Outstanding at end of period	1 year 3 months 10 days
Exercisable at end of period	1 year 3 months 10 days
Aggregate Intrinsic Value
Outstanding at end of period	$ 684
Exercisable at end of period	$ 684