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Stock-Based Compensation Plans - Restricted stock activity (Details) - USD ($) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
The 2007 plan |  |  |  |
Number Outstanding |  |  |  |
Balance at the beginning of the period (in shares) | 396,595 | 525,356 | 515,130 |
Shares granted | 136,645 | 146,440 | 237,708 |
Shares vested | (213,528) | (275,201) | (221,732) |
Shares cancelled | (20,377) |  | (5,750) |
Balance at the end of the period (in shares) | 299,335 | 396,595 | 525,356 |
Intrinsic value of unvested awards (in dollars) | $ 6,058,336 | $ 7,131,200 | $ 8,786,611 | $ 7,060,474
The 2007 plan | Restricted stock |  |  |  |
Number Outstanding |  |  |  |
Balance at the beginning of the period (in shares) | 396,595 | 525,356 | 515,130 |
Shares vested | (213,528) | (275,201) | (221,732) |
Shares cancelled | (20,377) |  | (5,750) |
Balance at the end of the period (in shares) | 299,335 | 396,595 | 525,356 |
Remaining average vesting period for recognition of unrecognized compensation expense | 1 year 6 months |  |  |
Unrecognized compensation expense (in dollars) | $ 3,800,000 |  |  |
The 2007 plan | Restricted stock | Awards Vesting Over Two Year Member |  |  |  |
Number Outstanding |  |  |  |
Shares granted | 20,000 |  |  |
Vesting period | 2 years |  |  |
The 2007 plan | Restricted stock | Awards Vesting Over Three Years [Member] |  |  |  |
Number Outstanding |  |  |  |
Shares granted | 85,000 | 125,000 | 174,500 |
Vesting period | 3 years | 3 years | 3 years |
The 2007 plan | Restricted stock | Awards vesting over four years [Member] |  |  |  |
Number Outstanding |  |  |  |
Shares granted | 13,250 | 5,000 | 13,000 |
Vesting period | 4 years | 4 years | 4 years |
The 2007 plan | Restricted stock | Awards vesting on first anniversary |  |  |  |
Number Outstanding |  |  |  |
Shares granted |  | 16,440 | 50,208 |
The 2007 plan | Restricted Stock Four Year Vesting [Member] | Awards vesting on first anniversary |  |  |  |
Number Outstanding |  |  |  |
Shares granted | 18,395 |  |  |
1996 Plan |  |  |  |
Number Outstanding |  |  |  |
Vesting period | 10 years |  |  |

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- Definition Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, 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 (i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation. + References No definition available. + Details
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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 number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period. + 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 The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target 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)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date. + 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)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
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- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period. + 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)(2)(iii)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Intrinsic value of equity-based compensation awards not vested. Excludes stock and unit options. + References No definition available. + Details
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