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Income Taxes - Income Tax Reconciliation (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2017 | Sep. 30, 2017 | Jun. 30, 2017 | Mar. 31, 2017 | Dec. 31, 2016 | Sep. 30, 2016 | Jun. 30, 2016 | Mar. 31, 2016 | Dec. 31, 2015 | Sep. 30, 2015 | Jun. 30, 2015 | Mar. 31, 2015 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Operating Loss Carryforwards [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Expected tax (benefit)/expense |  |  |  |  |  |  |  |  |  |  |  |  | $ 0.0 | $ 0.0 | $ 0.0
Overseas statutory tax rates differential |  |  |  |  |  |  |  |  |  |  |  |  | (41.5) | (19.3) | 6.4
Prior year adjustments |  |  |  |  |  |  |  |  |  |  |  |  | 1.3 | 3.3 | (4.5)
Valuation allowance |  |  |  |  |  |  |  |  |  |  |  |  | (37.9) | 21.0 | 11.8
Impact of unrecognized tax benefits |  |  |  |  |  |  |  |  |  |  |  |  | 0.1 | (1.9) | 0.0
Restricted foreign tax credits |  |  |  |  |  |  |  |  |  |  |  |  | 1.6 | 1.9 | 0.6
Share-based payments |  |  |  |  |  |  |  |  |  |  |  |  | (0.9) | 0.0 | 0.0
Foreign exchange |  |  |  |  |  |  |  |  |  |  |  |  | (2.1) | 0.2 | (0.4)
Non-deductible expenses |  |  |  |  |  |  |  |  |  |  |  |  | 0.4 | 0.8 | 1.7
Non-taxable items |  |  |  |  |  |  |  |  |  |  |  |  | (0.9) | (0.9) | (1.3)
Impact of changes in statutory tax rates |  |  |  |  |  |  |  |  |  |  |  |  | 64.5 | 1.0 | 0.1
Total income tax expense/(benefit) | $ (10.2) | $ (9.2) | $ 1.2 | $ 2.8 | $ (2.6) | $ 4.9 | $ 1.3 | $ 2.5 | $ 5.3 | $ 1.8 | $ 2.2 | $ 5.1 | (15.4) | 6.1 | $ 14.4
Effective Income Rate Tax Reconciliation, Tax Settlement, Foreign Credit, Amount |  |  |  |  |  |  |  |  |  |  |  |  | 0.3 | 3.2 |
Income tax examination, interest accrued | $ 0.4 |  |  |  | $ 1.3 |  |  |  |  |  |  |  | $ 0.4 | $ 1.3 |

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- Definition The amount of estimated interest accrued as of the balance sheet date arising from income tax examinations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319 + 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/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a),(b) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32639-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -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 + Details
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