Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2017

Retirement Benefits [Abstract]

Summary of the activity in the Option Plan

Below is a summary of the stock option activity in the Plans for the year ended December 31, 2017:

	2017
	Number of Stock Options Outstanding		Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Term	Aggregate Intrinsic value
					(in years)	(dollars in thousands)
Outstanding at January 1, 2017	1,083,667		$	12.61
Granted	210,977		20.40
Exercised	(333,959	)	13.49
Forfeited and Expired	(6,162	)	34.68
Outstanding at December 31, 2017	954,523		$	13.89	5.8	$	24,926
Vested and Exercisable at December 31, 2017	749,281		$	12.47	5.3	$	20,627

Schedule of assumptions used for valuing options granted with the Black-Scholes model

Options granted under the Option Plans during 2017, 2016 and 2015 were valued using the Black-Scholes model with the following average assumptions:

	Year Ended December 31,
	2017	2016	2015
Expected volatility	22.43% - 28.77%	21.98% - 26.88%	29.47%
Expected term	.33 - 6 Years	6.00 Years	6.00 Years
Expected dividends	None	None	None
Risk free rate	1.03% - 2.02%	1.32% - 1.83%	1.39%
Weighted-average grant date fair value	$19.66	$5.55	$4.73

Schedule of Other Share-based Compensation, Activity

Below is a summary of the restricted stock activity in the Plans for the years ended December 31, 2017:

	2017
	Shares		Weighted Average Grant-Date Fair Value per share
Unvested at the beginning of the year	370,334		$	23.53
Granted	201,544		38.70
Vested	(125,035	)	26.26
Forfeited	—		—
Unvested at the end of the year	446,843		$	29.61