Income Taxes - Change in Valuation Allowance (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019
Deferred Tax Valuation Allowance [Roll Forward]
Balance at beginning of period		$ 501.3	[1]	$ 557.9
Change in assessment	[2]	(50.3)		(8.3)
Current year operations, foreign currency and other		(36.2)		(48.3)
Balance at end of period	[1]	414.8		$ 501.3
Recognition of deferred tax asset due to release of valuation allowance		$ 51.5

[1] The movement in the valuation allowance balance differs from the amount in the effective tax rate reconciliation due to adjustments affecting balance sheet only items and foreign currency.

[2] Includes release of $51.5 million of valuation allowance against U.S. deferred tax assets in 2020.