Income Taxes - Income tax changes (Details) - USD ($) $ in Millions		12 Months Ended
Dec. 22, 2017	Dec. 31, 2018	Dec. 31, 2017
Income Taxes
Corporate tax rate (as a percent)	35.00%	21.00%
U.S. federal and state tax liability related to transition tax on repatriation of foreign earnings and profits			$ 52.2
Amount of deemed repatriation of foreign earnings and profits			946.0
Income tax benefit related to remeasurement of deferred tax assets and liabilities due to change in enacted tax rate			$ 301.2

Amount of accumulated earnings of foreign subsidiary deemed repatriated pursuant to Tax Cuts and Jobs Act of 2017.

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- Definition

Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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-Publisher FASB
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Amount of income tax expense (benefit) for remeasurement of deferred tax from change in tax rate pursuant to Tax Cuts and Jobs Act.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32639-109319

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Amount of tax liability from transition tax on accumulated earnings of controlled foreign corporation deemed repatriated pursuant to Tax Cuts and Jobs Act.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/topic&trid=2144680

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