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Income Taxes - Reconciliation of unrecognized tax benefits (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Reconciliation of the beginning and ending amount of unrecognized tax benefits |  |  |
Balance of unrecognized tax benefits, January 1 | $ 20.0 | $ 17.3 |
Additions for tax positions of prior years | 1.9 | 2.8 |
Additions based on tax positions related to the current year | 0.2 | 0.1 |
Reductions for tax positions of prior years | (4.2) | (0.2) |
Balance of unrecognized tax benefits, December 31 | 17.9 | 20.0 | $ 17.3
Income Taxes |  |  |
Deferred tax assets, uncertainty in income taxes | 2.0 | 2.0 |
Net amount of unrecognized tax benefits having impact on the effective tax rate for continuing operations | 15.9 | 18.0 |
Interest expense in the consolidated income statements | 0.1 | 0.5 | 0.6
Penalties in the consolidated income statements | 0.0 | 0.0 | $ 0.0
Accrued interest on the consolidated balance sheets | 0.8 | 0.7 |
Accrued penalties on the consolidated balance sheets | 0.0 | $ 0.0 |
Unrecognized tax benefits, decrease resulting from statute of limitations | $ 11.4 |  |

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- Definition Amount of unrecognized tax benefits. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 45 -Paragraph 10B -URI http://asc.fasb.org/extlink&oid=116821951&loc=SL37586934-109318 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319 + Details
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