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Stock-Based Compensation Plans (Tables) | 12 Months Ended
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Dec. 31, 2017
Stock-Based Compensation Plans |
Schedule of components of stock compensation expense |
|  | 2017 |  | 2016 |  | 2015 |
|  | (in thousands) |
2007 Stock Incentive Plan |  | $ | 4,207 |  | $ | 3,681 |  | $ | 4,102 |
Employee Stock Purchase Plan |  |  | 63 |  |  | 36 |  |  | 48 |
Total Stock Compensation Expense |  | $ | 4,270 |  | $ | 3,717 |  | $ | 4,150 |
Summary of restricted stock activity under the 2007 Plan |
|  |  |  | Weighted Average |  | Aggregate Grant |
|  | Number Outstanding |  | Grant Date Fair Value |  | Date Fair Value |
Balance as of December 31, 2014 |  | 525,356 |  | $ | 13.71 |  | $ | 8,786,611 |
Shares granted |  | 146,440 |  |  | 18.53 |  |  | 2,713,159 |
Shares forfeited |  | — |  |  | — |  |  | — |
Shares vested |  | (275,201) |  |  | 15.87 |  |  | (4,368,570) |
Balance as of December 31, 2015 |  | 396,595 |  | $ | 17.98 |  | $ | 7,131,200 |
Shares granted |  | 136,645 |  |  | 21.55 |  |  | 2,944,941 |
Shares forfeited |  | (20,377) |  |  | 17.79 |  |  | (362,536) |
Shares vested |  | (213,528) |  |  | 17.12 |  |  | (3,655,269) |
Balance as of December 31, 2016 |  | 299,335 |  | $ | 20.24 |  | $ | 6,058,336 |
Shares granted |  | 215,603 |  |  | 24.89 |  |  | 5,365,731 |
Shares forfeited |  | (10,999) |  |  | 24.38 |  |  | (268,200) |
Shares vested |  | (175,817) |  |  | 19.61 |  |  | (3,448,628) |
Balance as of December 31, 2017 |  | 328,122 |  | $ | 23.49 |  | $ | 7,707,239 |

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- Definition Tabular disclosure of the amount of total share-based compensation cost, including the amounts attributable to each share-based compensation plan and any related tax benefits. + 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 (h)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Tabular disclosure of the changes in outstanding nonvested restricted stock units. + 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) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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