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Income Taxes - Narrative (Details) - Tradeweb Markets LLC - USD ($) | 3 Months Ended | 9 Months Ended
--- | --- | ---
Dec. 31, 2018 | Sep. 30, 2018
Successor | Federal |  |
Income Taxes |  |
Net operating loss carryforwards | $ 17,196,000 |
Successor | New York state |  |
Income Taxes |  |
Net operating loss carryforwards | 24,449,000 |
Successor | New York City |  |
Income Taxes |  |
Net operating loss carryforwards | 22,654,000 |
Successor | New York City | Tax periods from 2009 - 2013 | Accounts payable, accrued expenses and other liabilities |  |
Income Taxes |  |
Tax, penalties and interest expense | 26,000 |
Successor | New York City | Tax periods from 2012 - 2016 | Provision for income taxes |  |
Income Taxes |  |
Tax, penalties and interest provision | $ 70,000 |
Predecessor | New York City | Tax periods from 2009 - 2013 | Accounts payable, accrued expenses and other liabilities |  |
Income Taxes |  |
Tax, penalties and interest expense |  | $ 1,288,000
Predecessor | New York City | Tax periods from 2012 - 2016 | Provision for income taxes |  |
Income Taxes |  |
Tax, penalties and interest provision |  | $ 2,003,000

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