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Stock-Based Compensation Plans - Additional Information (Details) - USD ($) |  | 3 Months Ended |
--- | --- | --- | ---
May 24, 2007 | Mar. 31, 2019 | Mar. 31, 2018 | Apr. 01, 2018
Employee Stock Purchase Plan |  |  |  |
Stock-based compensation plans |  |  |  |
Number of shares authorized |  |  |  | 325,000
Maximum percentage of cash compensation allowed to be deducted for the purchase of common stock by eligible employees |  | 10.00% |  |
Maximum number of shares to be purchased by employee in one calendar year (in shares) |  | 1,000 |  |
Maximum amount of shares to be purchased by employee in one calendar year (in dollars) |  | $ 25,000 |  |
Purchase price expressed as a percentage of the market price of the common stock on the purchase date or on the date of entry |  | 85.00% |  |
Shares issued (in shares) |  | 6,732 | 5,497 |
2007 Stock Incentive Plan | Restricted Stock |  |  |  |
Stock-based compensation plans |  |  |  |
Shares granted (in shares) |  | 0 |  |
Number of shares authorized |  | 2,800,000 |  |
Stock options outstanding (in shares) |  | 0 |  |
Number of shares available for future issuance (in shares) |  | 890,730 |  |
2007 Stock Incentive Plan | Restricted Stock | Minimum |  |  |  |
Stock-based compensation plans |  |  |  |
Vesting period | 1 year |  |  |
2007 Stock Incentive Plan | Restricted Stock | Maximum |  |  |  |
Stock-based compensation plans |  |  |  |
Vesting period | 3 years |  |  |
2018 Plan | Restricted Stock |  |  |  |
Stock-based compensation plans |  |  |  |
Shares granted (in shares) |  | 0 |  |
Number of shares authorized |  | 800,000 |  |
2018 Plan | Restricted Stock | Minimum |  |  |  |
Stock-based compensation plans |  |  |  |
Vesting period |  | 1 year |  |
2018 Plan | Restricted Stock | Maximum |  |  |  |
Stock-based compensation plans |  |  |  |
Vesting period |  | 3 years |  |

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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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=109197908&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://fasb.org/us-gaap/role/ref/legacyRef -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=109197908&loc=d3e5070-113901 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition The highest quantity of shares an employee can purchase under the plan per period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=109197908&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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=109197908&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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition Number of options outstanding, including both vested and non-vested options. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -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=109197908&loc=d3e5070-113901 + Details
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- Definition Number of shares issued during the period as a result of an employee stock purchase plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(28)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition The maximum amount of shares an employee can purchase under the plan per period. + References No definition available. + Details
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- Definition Represents the maximum percentage of cash compensation allowed to be deducted each pay period for the purchase of common stock by eligible employees. + References No definition available. + Details
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