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Employee Benefit Plans - Additional Information (Details) - USD ($) |  |  | 12 Months Ended
--- | --- | --- | ---
Jan. 01, 2017 | Feb. 01, 2016 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Employee Benefit Plans |  |  |  |  |
Profit sharing contributions |  |  | $ 0 | $ 0 |
Employer matching contribution |  | 50.00% |  |  |
Contribution by employees |  | 4.00% |  |  |
Employer contribution to Plan |  |  | 1,500,000 | 655,000 |
Compensation expense |  |  | $ 1,294,000 | 899,000 |
Employee Stock Purchase Plan |  |  |  |  |
Employee Benefit Plans |  |  |  |  |
Common stock reserved and available for sale |  |  | 200,000 |  |
Compensation expense |  |  | $ 0 | $ 0 | $ 0
3% contributed by employees |  |  |  |  |
Employee Benefit Plans |  |  |  |  |
Employer matching contribution | 100.00% |  |  |  |
Contribution by employees | 3.00% |  |  |  |
2% contributed by employees |  |  |  |  |
Employee Benefit Plans |  |  |  |  |
Employer matching contribution | 50.00% |  |  |  |
Contribution by employees | 2.00% |  |  |  |

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- Definition Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 14.F) -URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5047-113901 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Aggregate number of common shares reserved for future issuance. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -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 Amount of cost for defined contribution plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942 + 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 Amount of discretionary contributions made by an employer to a defined contribution plan. + References No definition available. + Details
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- Definition Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan. + References No definition available. + Details
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