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Stock-Based Compensation Plans (Details Textual) - USD ($) $ / shares in Units, $ in Thousands | 3 Months Ended
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Mar. 31, 2018 | Mar. 31, 2017
Stock-based Compensation Plans (Textual) [Abstract] |  |
Share-based Compensation | $ 5,642 | $ 6,074
Cash received from employee stock purchase plan purchases | $ 2,000 | $ 1,900
2014 Long Term Incentive Plan [Member] |  |
Stock-based Compensation Plans (Textual) [Abstract] |  |
Expiry date for stock options grant | May 21, 2024 |
Shares available for grant under the incentive plan | 878,454 |
Employee Stock Purchase Plan [Member] |  |
Stock-based Compensation Plans (Textual) [Abstract] |  |
Expiry date for stock options grant | May 19, 2025 |
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent | 85.00% |
Shares available for grant under the incentive plan | 1,102,825 |
Shares authorized for issuance | 4,500,000 |
Shares issued to employee under purchase plan | 36,270 | 30,154
Weighted average fair value of employee stock purchase rights issued | $ 16.22 | $ 18.66
Maximum [Member] | Restricted Stock [Member] |  |
Stock-based Compensation Plans (Textual) [Abstract] |  |
Range Of Forfeiture Provisions | 5 years |

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- Definition The total cash inflow associated with the amount received from employees to purchase company stock, including stock option exercises. + References No definition available. + Details
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- Definition Weighted average fair value of employee stock purchase rights issued. + References No definition available. + Details
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- Definition The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585 + Details
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- Definition Date the equity-based award expires, in CCYY-MM-DD format. + 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)(2) -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 difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + 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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