Income Taxes - 2017 Tax Act (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2026	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
2017 Tax Act
Statutory Corporate tax rate (as a percent)				35.00%	35.00%	35.00%
Incremental income tax provision	$ 68.9
Estimated tax provision for the federal and state impacts of one-time deemed repatriation	55.0
Payment period for federal portion of toll charge liability				8 years
Toll charge liability recorded in long-term income tax liabilities	30.6			$ 30.6
Toll charge liability recorded in accrued income taxes (current)	2.7			$ 2.7
Estimated tax benefit for remeasurement of deferred tax assets and liabilities	1.4
Estimated tax provision for state income taxes and foreign withholding taxes	$ 12.5
Forecast
2017 Tax Act
Statutory Corporate tax rate (as a percent)			21.00%
Effective tax rate of GILTI on offshore earnings (as a percent)		13.125%	10.50%
Dividends received deduction on certain qualified dividends from foreign subsidiaries (as a percent)			100.00%