Share-Based Compensation Plan (Tables)

12 Months Ended

Dec. 31, 2014

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of stock options outstanding by exercise price range

The following summarizes information about stock options outstanding at December 31, 2014:

	Options Outstanding				Options Exercisable
Range of Exercise Prices Per Share	Number Outstanding	Weighted Average Exercise Price Per Share		Weighted Average Contractual Term (In Years)	Number Exercisable	Weighted Average Exercise Price Per Share		Weighted Average Contractual Term (In Years)
$ 19.43 - 21.10	107,803	$	20.36	5.58	107,803	$	20.36	5.58
23.78 - 25.14	625,420	24.57		6.17	376,259	24.44		5.03
29.45	183,038	29.45		9.17	—	—		0.00
32.28	121,050	32.28		0.97	121,050	32.28		0.97
$ 19.43 - 32.28	1,037,311	$	25.90	6.03	605,112	$	25.28	4.31

Summary of activity for Corporation's stock options

A summary of activity for the Corporation's stock options as of and during the three years ended December 31, 2014 is presented below:

	Non-Vested Stock Options Outstanding						Stock Options Outstanding
	Number of Options		Weighted- Average Exercise Price Per Share		Weighted- Average Grant Date Fair Value Per Share		Number of Options		Weighted- Average Exercise Price Per Share
Outstanding at December 31, 2011	162,883		$	21.27	$	6.55	815,119		$	28.29
Activity during 2012:
Granted	229,763		23.78		7.08		229,763		23.78
Exercised	—		—		—		(1,532	)	19.97
Vested	(76,103	)	21.55		6.63		—		—
Expired or forfeited	(1,778	)	21.48		6.62		(46,128	)	28.78
Outstanding at December 31, 2012	314,765		23.03		6.92		997,222		27.24
Activity during 2013:
Granted	244,719		25.14		7.40		244,719		25.14
Exercised	—		—		—		(100,145	)	22.87
Vested	(127,443	)	22.94		6.92		—		—
Expired or forfeited	(17,961	)	23.34		6.98		(67,806	)	32.27
Outstanding at December 31, 2013	414,080		24.29		7.19		1,073,990		26.84
Activity during 2014:
Granted	190,011		29.45		9.64		190,011		29.45
Exercised	—		—		—		(72,936	)	24.67
Vested	(148,016	)	23.43		6.98		—		—
Expired or forfeited	(23,876	)	25.67		7.79		(153,754	)	37.50
Outstanding at December 31, 2014	432,199		$	26.75	$	8.30	1,037,311		$	25.90
Exercisable/vested at December 31, 2014							605,112		$	25.28

Assumptions of Black-Scholes option pricing model

The fair value of the stock options granted was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions.

	2014		2013		2012
Expected dividend yield	3.00	%	3.50	%	3.60	%
Risk-free interest rate	2.16	%	1.34	%	1.18	%
Expected stock price volatility	42.2	%	42.1	%	44.4	%
Expected life of options — in years	7.00		7.00		6.11
Weighted average fair value per share	$9.64		$7.40		$7.08

Summary of activity for restricted stock units

A summary of the activity for restricted stock units during the three years ended December 31, 2014 is presented below:

	Number of Units		Weighted Average Grant Date Fair Value Per Unit
Outstanding at December 31, 2011	130,512		$	20.90
Activity during 2012:
Granted	69,772		22.20
Converted into shares of common stock	(35,346	)	23.27
Forfeited/expired	(8,428	)	23.05
Outstanding at December 31, 2012	156,510		20.83
Activity during 2013:
Granted	71,768		23.42
Converted into shares of common stock	(36,416	)	22.44
Forfeited/expired	(3,330	)	21.67
Outstanding at December 31, 2013	188,532		21.49
Activity during 2014:
Granted	73,468		27.49
Converted into shares of common stock	(52,008	)	19.23
Forfeited/expired	(5,673	)	24.31
Outstanding at December 31, 2014	204,319		$	24.14