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Income Taxes - Income Tax Reconciliation (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Operating Loss Carryforwards [Line Items] |  |  |
Income tax benefit at statutory tax rate of zero percent | $ 0.0 | $ 0.0 | $ 0.0
Overseas statutory tax rates differential | 12.1 | (21.2) | (17.1)
Base erosion and anti-abuse tax (BEAT) expense | 4.3 | 0.3 | 6.0
Prior year adjustments | (3.2) | (1.7) | 1.4
Change in valuation allowance (2) | (10.4) | 42.6 | 7.1
Impact of unrecognized tax benefits | 0.0 | 0.0 | (12.8)
Restricted foreign tax credits | 0.0 | 1.5 | 0.0
Australian non-resident withholding tax | 1.0 | 1.0 | 4.4
Share-based payments | 0.0 | (0.6) | 0.2
Foreign exchange | 1.9 | 0.0 | 0.1
Non-deductible expenses | 4.6 | 0.0 | 0.7
Non-taxable items | 0.0 | (0.1) | (0.3)
Impact of changes in statutory tax rates | (1.7) | 1.1 | 0.1
Total tax expense/(benefit) | 8.6 | 22.9 | $ (10.2)
U.S branch of Aspen U.K. |  |  |
Operating Loss Carryforwards [Line Items] |  |  |
Valuation allowance, associated losses | 20.9 | 9.9 |
Valuation allowance, use of existing net operating losses | 14.0 |  |
Lloyds syndicate |  |  |
Operating Loss Carryforwards [Line Items] |  |  |
Valuation allowance, associated losses | $ 10.4 | $ 28.2 |

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- Definition U.S Base Erosion Anti-Abuse Tax (BEAT) on premiums ceded from U.S. subsidiaries to non-U.S. related parties. + References No definition available. + Details
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