Derivative Instruments and Fair Value Accounting FX Hedge (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended
		Sep. 30, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Foreign Currency Fair Value Hedge Derivative [Line Items]
Total stockholders' equity		$ 2,093.6	$ 2,093.6	$ 2,160.4	$ 2,466.1	$ 2,378.9	$ 2,459.3	$ 2,529.6	$ 2,565.1	$ 2,562.0
Foreign Exchange Contract [Member] | Designated as Hedging Instrument [Member]
Foreign Currency Fair Value Hedge Derivative [Line Items]
Derivative, Notional Amount		55.0	55.0
Derivative Liability		2.1	2.1
Foreign Exchange Contract [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Designated as Hedging Instrument [Member]
Foreign Currency Fair Value Hedge Derivative [Line Items]
Total stockholders' equity		(2.3)	(2.3)
Foreign Exchange Contract [Member] | Interest Expense [Member] | Designated as Hedging Instrument [Member]
Foreign Currency Fair Value Hedge Derivative [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net		2.3	4.1
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net	[1]	$ (2.3)	$ (2.3)

[1] (Mark One)