Share-Based Compensation Plan (Tables)

12 Months Ended

Dec. 31, 2015

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, 2015:

	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)
$10.56 - 15.84	84,775	$	13.31	4.73	84,775	$	13.31	4.73
19.97 - 21.10	74,189	20.47		4.40	74,189	20.47		4.40
23.78 - 25.14	502,845	24.63		5.08	384,912	24.47		4.44
29.45 - 30.18	392,930	29.88		8.76	31,108	29.45		8.17
$10.56 - 30.18	1,054,739	$	25.38	6.38	574,984	$	22.58	4.68

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, 2015 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, 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
Activity during 2015:
Granted	244,165		30.18		8.40		244,165		30.18
Lake Michigan converted options	—		—		—		132,883		12.93
Exercised	—		—		—		(310,985	)	25.10
Vested	(150,224	)	25.57		7.80		—		—
Expired or forfeited	(46,385	)	27.99		8.50		(48,635	)	28.18
Outstanding at December 31, 2015	479,755		$	28.75	$	8.49	1,054,739		$	25.38
Exercisable/vested at December 31, 2015							574,984		$	22.58

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.

	2015		2014		2013
Expected dividend yield	3.50	%	3.00	%	3.50	%
Risk-free interest rate	1.78	%	2.16	%	1.34	%
Expected stock price volatility	39.1	%	42.2	%	42.1	%
Expected life of options — in years	7.0		7.0		7.0
Weighted average fair value per share	$8.40		$9.64		$7.40

Summary of activity for restricted stock units

A summary of the activity for restricted stock units during the three years ended December 31, 2015 is presented below:

	Number of Units		Weighted Average Grant Date Fair Value Per Unit
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
Activity during 2015:
Granted	85,645		28.52
Converted into shares of common stock	(70,166	)	22.51
Forfeited/expired	(11,809	)	25.61
Outstanding at December 31, 2015	207,989		$	26.41