Benefit Plans - Option Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Additional disclosure
Intrinsic value	$ 8,400	$ 7,700	$ 2,000
Compensation expense	$ 571	$ 927	$ 883
Stock option
Number of Stock Options Outstanding
Options outstanding at the beginning of the year (in shares)	954,523
Granted (in shares)	0
Exercised (in shares)	(255,178)
Forfeited and expired (in shares)	(17,412)
Options outstanding at the end of the year (in shares)	681,933	954,523
Vested at the end of the year (in shares)	635,396
Weighted Average Exercise Price Per Share
Options outstanding at the beginning of the year (in dollars per share)	$ 13.89
Granted (in dollars per share)	0.00
Exercised (in dollars per share)	9.71
Forfeited and expired (in dollars per share)	21.53
Options outstanding at the end of the year (in dollars per share)	15.26	$ 13.89
Vested at the end of the year (in dollars per shares)	$ 15.11
Weighted average remaining contractual life
Outstanding at the end of the year	5 years 3 months 4 days
Vested at the end of the year	5 years 15 days
Additional disclosure
Aggregate intrinsic value, outstanding	$ 6,962
Aggregate Intrinsic value, vested and expected to vest	6,715
Unrecognized compensation expense	$ 134