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Summary of Significant Accounting Policies - Employee related obligations Revenue and Sales and marketing (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018
Summary of Significant Accounting Policies |  |
Amount of contributions made to the plan |  | $ 0.0
Amount of approved contribution to the plan | $ 0.3 |
Premium deficiency | 0.0 |
Advertising expenses | $ 76.0 | $ 36.2

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