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Derivative Financial Instruments - Additional Information (Details) £ in Millions, $ in Millions	Dec. 31, 2019 USD ($) derivative	Dec. 31, 2018 USD ($) derivative $ / unit	Dec. 31, 2018 GBP (£) derivative $ / unit
Derivative [Line Items]
Number of contracts with a contingent feature in a net liability position | derivative	0
Other Assets
Derivative [Line Items]
Derivative asset, gross	$ 2.2	$ 0.9
Other Liabilities
Derivative [Line Items]
Derivative liability, gross	1.0	$ 1.4
Forward contracts
Derivative [Line Items]
Derivative, number of contracts | derivative		2	2
Cash collateral held from counterparty	8.7	$ 3.1
Cash collateral held at counterparty	0.0	$ 28.0
Collar contracts
Derivative [Line Items]
Derivative, number of contracts | derivative		2	2
Foreign contracts and collar contracts | Other Assets
Derivative [Line Items]
Derivative asset, net	$ 5.6	$ 4.9
Designated as Hedging Instrument | Net Investment Hedging | Forward contract expiring in June 2021
Derivative [Line Items]
Derivative, notional amount		450.0	£ 325.3
Designated as Hedging Instrument | Net Investment Hedging | Forward contract expiring in February 2024
Derivative [Line Items]
Derivative, notional amount		$ 400.0	£ 285.8
Designated as Hedging Instrument | Net Investment Hedging | Collar contract-call option | Minimum
Derivative [Line Items]
Derivative, option strike price (in dollars per unit) | $ / unit		1.318	1.318
Designated as Hedging Instrument | Net Investment Hedging | Collar contract-call option | Maximum
Derivative [Line Items]
Derivative, option strike price (in dollars per unit) | $ / unit		1.448	1.448
Designated as Hedging Instrument | Net Investment Hedging | Collar contract-put option | Minimum
Derivative [Line Items]
Derivative, option strike price (in dollars per unit) | $ / unit		1.288	1.288
Designated as Hedging Instrument | Net Investment Hedging | Collar contract-put option | Maximum
Derivative [Line Items]
Derivative, option strike price (in dollars per unit) | $ / unit		1.535	1.535

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Derivative, Net Liability Position, Number of Instruments

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Fair value of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, not subject to a master netting arrangement.

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The strike price on the foreign currency option contract such as a put option or a call option.

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Nominal or face amount used to calculate payments on the derivative liability.

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