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Compensation and Other Benefit Plans - ESPP (Details) - 2015 ESPP - shares | 1 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | ---
May 31, 2017 | Dec. 31, 2019 | Dec. 31, 2018 | Apr. 30, 2017 | May 31, 2015
Share-based compensation |  |  |  |  |
Percentage related to employees to purchase shares at the lower fair market value at offering period |  | 85.00% |  |  |
Common stock reserved for future issuance (in shares) |  |  |  |  | 15,000
Offering period |  | 6 months |  |  |
Percentage of compensation of eligible employees to purchase shares of entity common stock at discount through payroll deductions |  | 10.00% |  |  |
Common Stock |  |  |  |  |
Share-based compensation |  |  |  |  |
Increase in aggregate number of shares authorized for issuance | 250,000 |  |  |  |
Shares authorized for issuance | 265,000 |  |  | 15,000 |
Maximum shares per employee | 2,500 |  |  |  |
Shares purchased (in shares) |  | 2,365 | 2,948 |  |

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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=116856206&loc=d3e5070-113901 + Details
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- Definition Number of shares authorized for issuance under share-based payment arrangement. + 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=116856206&loc=d3e5070-113901 + Details
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- Definition Number of shares purchased for issuance under share-based payment arrangement. + 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=116856206&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 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5047-113901 + Details
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