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Stock-Based Compensation - Narrative (Details) - USD ($) |  | 1 Months Ended | 7 Months Ended |
--- | --- | --- | --- | ---
Jun. 13, 2017 | Jun. 30, 2016 | Dec. 31, 2017 | Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
ESPP employee contributions |  |  | $ 1,419,000 | $ 0
Employee Stock Purchase Plan |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
ESPP employee contributions |  |  | $ 1,400,000 |
Class A Common Stock | Employee Stock Purchase Plan |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Number of shares available for grant |  |  | 5,000,000 |
Purchase price of common stock, percentage of fair market value | 85.00% |  |  |
Maximum stock purchase value, per employee |  |  | $ 12,500 |
Stock purchase offering period |  |  | 6 months |
Shares purchased during period |  |  | 0 |
Shares distributed during period |  |  | 0 |
Class A Common Stock | 2014 Equity Incentive Plan |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Number of additional shares authorized |  | 3,900,000 |  |
Number of shares available for grant |  |  | 1,999,415 |

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- Definition Carrying value as of the balance sheet date of obligations, excluding pension and other postretirement benefits, incurred through that date and payable for perquisites provided to employees pertaining to services received from them. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). + 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 210.5-02.20) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=82887183&loc=d3e6935-107765 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=82887183&loc=d3e6911-107765 + Details
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