Fair Value Measurements and the Fair Value Option - Derivatives Financial Instruments (Details) € in Millions, £ in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 GBP (£)	Sep. 30, 2019 EUR (€)	Dec. 31, 2018 USD ($)
Derivative [Line Items]
Unrealized (losses) gains, arising during the period			$ 12.9
Hedge Asset	$ 64.6		64.6				$ 43.7
Interest Expense	51.8	$ 55.2	162.8	$ 181.3
Cash Received (Paid)
Deferred taxes on unrealized gains (losses), arising during the period			(8.8)
Foreign Currency Translation [Member]
Derivative [Line Items]
Unrealized (losses) gains, arising during the period			(37.2)
Cash Received (Paid)
Deferred taxes on unrealized gains (losses), arising during the period			0.8
Foreign Exchange Contract [Member] | Currency Derivative Contracts [Member]
Derivative [Line Items]
Unrealized (losses) gains, arising during the period			52.6
Cash Received (Paid)
Deferred taxes on unrealized gains (losses), arising during the period			(10.2)
Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member] | Level 2 [Member]
Derivative [Line Items]
Hedge Asset	64.6		64.6
Hedge Liability	(52.0)		(52.0)
Unrealized currency derivative contracts (loss) gain			52.7
Realized Gains (Losses)			10.8
Cash Received (Paid)
Total			34.2
Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member] | Level 2 [Member] | Interest Expense [Member]
Derivative [Line Items]
Interest Expense			5.0
Designated as Hedging Instrument [Member] | Derivatives Outstanding [Member] | Level 2 [Member]
Derivative [Line Items]
Hedge Asset	64.6		64.6
Hedge Liability	(52.0)		(52.0)
Unrealized currency derivative contracts (loss) gain			45.2
Realized Gains (Losses)			10.7
Cash Received (Paid)
Cash Paid			0.0
Designated as Hedging Instrument [Member] | Derivatives Outstanding [Member] | Level 2 [Member] | Interest Expense [Member]
Derivative [Line Items]
Interest Expense			4.7
Designated as Hedging Instrument [Member] | Foreign Exchange Contract, One [Member]
Derivative [Line Items]
Notional Amount | €						€ 175.0
Designated as Hedging Instrument [Member] | Foreign Exchange Contract, One [Member] | Level 2 [Member]
Derivative [Line Items]
Hedge Asset	15.5		15.5
Hedge Liability	(0.2)		(0.2)
Unrealized currency derivative contracts (loss) gain			1.7
Realized Gains (Losses)			10.7
Cash Received (Paid)
Cash Paid			0.0
Designated as Hedging Instrument [Member] | Foreign Exchange Contract, One [Member] | Level 2 [Member] | Interest Expense [Member]
Derivative [Line Items]
Interest Expense			1.8
Designated as Hedging Instrument [Member] | Foreign Exchange Contract, Two [Member] | KWE [Member]
Derivative [Line Items]
Notional Amount | €						€ 240.8
Designated as Hedging Instrument [Member] | Foreign Exchange Contract, Two [Member] | Level 2 [Member] | KWE [Member]
Derivative [Line Items]
Hedge Asset	0.0		0.0
Hedge Liability	(51.8)		(51.8)
Unrealized currency derivative contracts (loss) gain			6.2
Realized Gains (Losses)			0.0
Cash Received (Paid)
Cash Paid			0.0
Designated as Hedging Instrument [Member] | Foreign Exchange Contract, Two [Member] | Level 2 [Member] | KWE [Member] | Interest Expense [Member]
Derivative [Line Items]
Interest Expense			0.0
Designated as Hedging Instrument [Member] | Foreign Exchange Contract, Three [Member] | Level 2 [Member] | KWE [Member]
Derivative [Line Items]
Hedge Asset	0.0		0.0
Hedge Liability	0.0		0.0
Unrealized currency derivative contracts (loss) gain			7.4
Realized Gains (Losses)			0.0
Cash Received (Paid)
Cash Paid			0.0
Designated as Hedging Instrument [Member] | Foreign Exchange Contract, Three [Member] | Level 2 [Member] | KWE [Member] | Interest Expense [Member]
Derivative [Line Items]
Interest Expense			0.0
Designated as Hedging Instrument [Member] | Foreign Exchange Contract, Four [Member]
Derivative [Line Items]
Notional Amount | £					£ 630.0
Designated as Hedging Instrument [Member] | Foreign Exchange Contract, Four [Member] | Level 2 [Member]
Derivative [Line Items]
Hedge Asset	49.1		49.1
Hedge Liability	0.0		0.0
Unrealized currency derivative contracts (loss) gain			29.9
Realized Gains (Losses)			0.0
Cash Received (Paid)
Cash Paid			0.0
Designated as Hedging Instrument [Member] | Foreign Exchange Contract, Four [Member] | Level 2 [Member] | Interest Expense [Member]
Derivative [Line Items]
Interest Expense			2.9
Designated as Hedging Instrument [Member] | Derivative Settled [Member] | Level 2 [Member]
Derivative [Line Items]
Hedge Asset	0.0		0.0
Hedge Liability	0.0		0.0
Unrealized currency derivative contracts (loss) gain			7.5
Realized Gains (Losses)			0.1
Cash Received (Paid)
Cash Received			34.2
Designated as Hedging Instrument [Member] | Derivative Settled [Member] | Level 2 [Member] | Interest Expense [Member]
Derivative [Line Items]
Interest Expense			0.3
Designated as Hedging Instrument [Member] | Foreign Exchange Contract, Five [Member] | Level 2 [Member]
Derivative [Line Items]
Hedge Asset	0.0		0.0
Hedge Liability	0.0		0.0
Unrealized currency derivative contracts (loss) gain			2.4
Realized Gains (Losses)			0.1
Cash Received (Paid)
Cash Received			2.9
Designated as Hedging Instrument [Member] | Foreign Exchange Contract, Five [Member] | Level 2 [Member] | Interest Expense [Member]
Derivative [Line Items]
Interest Expense			0.0
Designated as Hedging Instrument [Member] | Foreign Exchange Contract, Six [Member] | Level 2 [Member]
Derivative [Line Items]
Hedge Asset	0.0		0.0
Hedge Liability	$ 0.0		0.0
Unrealized currency derivative contracts (loss) gain			5.1
Realized Gains (Losses)			0.0
Cash Received (Paid)
Cash Received			31.3
Designated as Hedging Instrument [Member] | Foreign Exchange Contract, Six [Member] | Level 2 [Member] | Interest Expense [Member]
Derivative [Line Items]
Interest Expense			$ 0.3