Share-Based Compensation Plan (Tables)

12 Months Ended

Dec. 31, 2012

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, 2012:

	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	166,779	$	20.43	7.47	101,288	$	20.74	6.93
23.78 - 24.86	521,311	24.28		6.96	272,037	24.69		5.07
32.28	131,000	32.28		2.97	131,000	32.28		2.97
35.67	48,720	35.67		0.95	48,720	35.67		0.95
39.69	129,412	39.69		1.95	129,412	39.69		1.95
$19.43 - 39.69	997,222	$	27.24	5.58	682,457	$	29.19	4.06

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, 2012 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 January 1, 2010	169,073		$	23.17	$	6.68	720,375		$	30.02
Activity during 2010:
Issued in OAK acquisition	—		—		—		26,425		26.83
Granted	60,365		24.56		7.65		60,365		24.56
Exercised	—		—		—		(1,736	)	23.63
Vested	(99,540	)	23.84		6.87		—		—
Forfeited/expired	(3,228	)	23.70		7.07		(47,764	)	31.08
Outstanding at December 31, 2010	126,670		23.29		6.99		757,665		29.42
Activity during 2011:
Granted	99,172		19.95		6.12		99,172		19.95
Exercised	—		—		—		—		—
Vested	(62,959	)	23.27		6.76		—		—
Forfeited/expired	—		—		—		(41,718	)	28.96
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		—		—
Forfeited/expired	(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
Exercisable/vested at December 31, 2012							682,457		$	29.19

Assumptions of Black-Scholes option pricing model

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

	2012		2011		2010
Expected dividend yield	3.60	%	3.50	%	3.50	%
Risk-free interest rate	1.18	%	2.76	%	3.37	%
Expected stock price volatility	44.4	%	42.0	%	41.1	%
Expected life of options — in years	6.11		6.10		6.33
Weighted average fair value per share	$7.08		$6.12		$7.65

Summary of activity for restricted stock units

A summary of the activity for restricted stock units during the three years ended December 31, 2012 is presented below:

	Number of Units		Weighted Average Grant Date Fair Value Per Unit
Outstanding at January 1, 2010	71,576		$	19.38
Activity during 2010:
Granted	40,629		22.62
Canceled (2009 grant)	(41,248	)	18.04
Modified (2009 grant)	41,248		23.25
Forfeited/expired	(31,353	)	21.26
Outstanding at December 31, 2010	80,852		22.94
Activity during 2011:
Granted	52,087		17.87
Converted into shares of common stock	(2,427	)	23.70
Forfeited/expired	—		—
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