Benefit Plans - Option Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Additional disclosure
Aggregate intrinsic value, outstanding	$ 24,639
Aggregate Intrinsic value, vested and expected to vest	18,094
Aggregate exercisable, intrinsic value	18,094
Intrinsic value	2,000	$ 100	$ 500
Compensation expense	$ 883	$ 905	$ 514
Stock option
Number of Stock Options Outstanding
Options outstanding at the beginning of the year (in shares)	1,059,086
Granted (in shares)	155,000
Exercised (in shares)	(117,750)
Forfeited and expired (in shares)	(12,669)
Options outstanding at the end of the year (in shares)	1,083,667	1,059,086
Vested at the end of the year (in shares)	716,651
Exercisable at the end of the year (in shares)	716,651
Weighted Average Exercise Price Per Share
Options outstanding at the beginning of the year (in dollars per share)	$ 11.35
Granted (in dollars per share)	20.51
Exercised (in dollars per share)	11.39
Forfeited and expired (in dollars per share)	14.58
Options outstanding at the end of the year (in dollars per share)	12.61	$ 11.35
Vested at the end of the year (in dollars per shares)	10.10
Options exercisable at the end of the year (in dollars per share)	$ 10.10
Weighted average remaining contractual life
Outstanding at the end of the year	6 years 2 months 2 days
Vested at the end of the year	5 years 1 month 2 days
Exercisable at the end of the year	5 years 1 month 2 days
Additional disclosure
Unrecognized compensation expense	$ 1,000