Stock Based Compensation (Tables)

12 Months Ended

Dec. 31, 2015

Dec. 31, 2013

Stock Based Compensation [Abstract]

Schedule of Share-based Payment Award, Restricted Stock, Valuation Assumptions [Table Text Block]

The following is a summary of the key assumptions used in the valuation calculations for market based awards granted during the years ended December 31, 2015, 2014, and 2013:

	2015	2014	2013
Risk free rate - minimum	0.10%	0.02%	0.07%
Risk free rate - maximum	1.05%	0.80%	0.17%
Dividend yield	3.932%	4.755%	4.269%
Volatility - minimum	15.41%	18.31%	16.40%
Volatility - maximum	16.04%	20.48%	20.92%
Service period	3 years	3 years	4 years

Nonvested Restricted Stock Shares Activity [Table Text Block]

A summary of the status of the nonvested restricted shares as of December 31, 2015, and the changes for the year ended December 31, 2015, is presented below:

Nonvested Shares	Shares		Weighted Average Grant-Date Fair Value
Nonvested at January 1, 2015	145,049		$	63.25
Issued	93,356		72.54
Vested	(49,156	)	58.08
Forfeited	(1,308	)	65.88
Nonvested at December 31, 2015	187,941		$	63.36

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

The following is a summary of the key assumptions used in the Black-Scholes valuation calculations for stock options granted during the year ended December 31,2013:

	2013
Term - minimum	0.25 years
Term - maximum	5.50 years
Risk free rate - minimum	0.02%
Risk free rate - maximum	1.55%
Dividend yield	4.21%
Volatility - minimum	15.60%
Volatility - maximum	46.29%

Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]

A summary of the status of the stock options as of December 31, 2015 and the changes for the year ended December 31, 2015 is presented below:

Stock Options	Options		Weighted Average Exercise Price
Outstanding at January 1, 2015	74,454		$	82.33
Granted	—		—
Exercised	(7,342	)	57.23
Expired	(9,000	)	76.87
Outstanding at December 31, 2015	58,112		$	86.21