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Income Taxes - Income Tax Reconciliation (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Operating Loss Carryforwards [Line Items] |  |  |
Expected tax (benefit)/expense | $ 0.0 | $ 0.0 | $ 0.0
Overseas statutory tax rates differential | (21.2) | (17.1) | (41.5)
Base erosion and anti-abuse tax (BEAT) expense | 0.3 | 6.0 | 0.0
Prior year adjustments | (1.7) | 1.4 | 1.3
Valuation allowance (2) | 42.6 | 7.1 | (37.9)
Impact of unrecognized tax benefits | 0.0 | (12.8) | 0.1
Restricted foreign tax credits | 1.5 | 0.0 | 0.7
Australian non-resident withholding tax | 1.0 | 4.4 | 0.9
Share-based payments | (0.6) | 0.2 | (0.9)
Foreign exchange | 0.0 | 0.1 | (2.1)
Non-deductible expenses | 0.0 | 0.7 | 0.4
Non-taxable items | (0.1) | (0.3) | (0.9)
Impact of changes in statutory tax rates | 1.1 | 0.1 | 64.5
Total tax expense/(benefit) | 22.9 | $ (10.2) | $ (15.4)
U.S branch of Aspen U.K. |  |  |
Operating Loss Carryforwards [Line Items] |  |  |
Valuation allowance, associated losses | 9.9 |  |
Lloyds syndicate |  |  |
Operating Loss Carryforwards [Line Items] |  |  |
Valuation allowance, associated losses | $ 28.2 |  |

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- Definition Effective Income Tax Rate Reconciliation, Tax Settlement, Non-Resident Withholding Tax, Amount + References No definition available. + Details
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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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- Definition Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 22 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08(h)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 20 -Section 45 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=109238882&loc=d3e38679-109324 + Details
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- Definition Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to increase (decrease) in the valuation allowance for deferred tax assets. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 45 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=116821951&loc=d3e32123-109318 + Details
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