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Stock-Based Compensation Plans (Details) - USD ($) | 3 Months Ended | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Dec. 31, 2015 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012 | May. 28, 2015 | May. 20, 2010 | May. 24, 2007 | Jun. 30, 2006
The 2007 plan |  |  |  |  |  |  |  |  |
Stock-based compensation plans |  |  |  |  |  |  |  |  |
Number of shares authorized | 2,800,000 | 2,800,000 |  |  |  | 800,000 |  | 2,000,000 |
Options |  |  |  |  |  |  |  |  |
Options cancelled (in shares) | 135,368 |  |  |  |  |  |  |  |
Outstanding at the end of the period (in shares) | 671,656 | 671,656 |  |  |  |  |  |  |
1996 Plan |  |  |  |  |  |  |  |  |
Stock-based compensation plans |  |  |  |  |  |  |  |  |
Number of shares authorized |  |  |  |  |  |  |  |  | 3,025,000
Vesting period |  | 10 years |  |  |  |  |  |  |
Vesting rate (as a percent) |  | 25.00% |  |  |  |  |  |  |
Period of beginning of vesting of awards from grant date |  | 1 year |  |  |  |  |  |  |
Total intrinsic value of options exercised (in dollars) |  | $ 300,000 | $ 200,000 | $ 400,000 |  |  |  |  |
Options |  |  |  |  |  |  |  |  |
Outstanding at the beginning of the period (in shares) |  | 49,000 | 75,437 | 136,928 |  |  |  |  |
Options exercised (in shares) |  | (49,000) | (26,437) | (54,991) |  |  |  |  |
Options cancelled (in shares) |  |  |  | (6,500) |  |  |  |  |
Outstanding at the end of the period (in shares) | 0 | 0 | 49,000 | 75,437 | 136,928 |  |  |  |
Options exercisable at the end of the period (in shares) |  |  | 49,000 | 75,437 |  |  |  |  |
Weighted Average Exercise Price |  |  |  |  |  |  |  |  |
Outstanding at the beginning of the period (in dollars per share) |  | $ 9.20 | $ 9.38 | $ 8.60 |  |  |  |  |
Options exercised (in dollars per share) |  | $ 9.20 | 9.71 | 7.96 |  |  |  |  |
Options cancelled (in dollars per share) |  |  |  | 5.01 |  |  |  |  |
Outstanding at the end of the period (in dollars per share) |  |  | 9.20 | 9.38 | $ 8.60 |  |  |  |
Options exercisable at the end of the period (in dollars per share) |  |  | $ 9.20 | $ 9.38 |  |  |  |  |
Weighted Average Remaining Contractual Term |  |  |  |  |  |  |  |  |
Outstanding at the end of the period |  |  | 7 months 2 days | 1 year 5 months 27 days | 2 years 2 months 23 days |  |  |  |
Options exercisable at the end of the period |  |  | 7 months 2 days | 1 year 5 months 27 days |  |  |  |  |
Aggregate Intrinsic Value |  |  |  |  |  |  |  |  |
Outstanding at the end of the period (in dollars) |  |  | $ 622,300 | $ 601,991 | $ 781,692 |  |  |  |
Options exercisable at the end of the period (in dollars) |  |  | $ 622,300 | $ 601,991 |  |  |  |  |
Employee Stock Purchase Plan |  |  |  |  |  |  |  |  |
Stock-based compensation plans |  |  |  |  |  |  |  |  |
Number of shares authorized |  |  |  |  |  |  | 250,000 |  |
Restricted stock | The 2007 plan |  |  |  |  |  |  |  |  |
Stock-based compensation plans |  |  |  |  |  |  |  |  |
Number of shares authorized | 2,263,712 | 2,263,712 |  |  |  |  |  |  |

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- Definition Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(3) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Number of options outstanding, including both vested and non-vested options. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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