Stock Option Plan and Stock Grants (Tables)

12 Months Ended

Dec. 31, 2013

Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block]

	Number of Shares		Weighted Average Grant Date Fair Value
Balance at December 31, 2010	104,686		$	18.61
Shares granted	239,330		28.75
Shares canceled/forfeited	(22,666	)	28.70
Shares vested	(227,330	)	24.50
Balance at December 31, 2011	94,020		27.75
Shares granted	214,664		35.06
Shares canceled/forfeited	(36,666	)	35.07
Shares vested	(177,998	)	32.30
Balance at December 31, 2012	94,020		32.97
Shares granted	173,332		37.32
Shares vested	(167,564	)	34.97
Balance at December 31, 2013	99,788		37.17

Summary of Stock Option Activity

A summary of our stock option activity, and related information for the years ended December 31, 2013, 2012, and 2011 follows:

	Shares Subject To Options		Weighted Average Exercise Price Per Share		Weighted Average Outstanding Contractual Life (in years)
Balance at December 31, 2010	1,610,368		$	20.16	4.9
Options canceled	(344,768	)	13.14
Balance at December 31, 2011	1,265,600		22.07		4.9
Options exercised	(160,000	)	24.10
Balance at December 31, 2012	1,105,600		21.78		4.0
Options exercised	(20,000	)	12.34
Balance at December 31, 2013	1,085,600		21.95		3.1
Exercisable at December 31, 2013	1,085,600		21.95		3.1