Employee Stock Plans (Tables) |
12 Months Ended | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Dec. 31, 2016 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Disclosure of Compensation Related Costs, Share-based Payments [Abstract] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block] | The following information relates to the stock option activity for the year ended December 31, 2016:
The aggregate intrinsic value in the table above represents the total pre-tax intrinsic value (the difference between the company's closing stock price on the last trading day of 2016 and the exercise price, multiplied by the number of in-the-money options) received by the option holders had all option holders exercised their options on December 31, 2016. This amount changes based on the market value of the company's stock. |
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Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] | The fair value of stock options was estimated using the Black-Scholes valuation model with the following weighted-average assumptions for the years ended December 31:
There is no expected dividend yield. |
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Schedule of Nonvested Share Activity [Table Text Block] | The following information summarizes the changes in non-vested performance shares, performance units, restricted stock, and restricted stock units for 2016:
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