Derivative Instruments and Hedging Activities (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019
Derivative [Line Items]
Remaining maturity of forward foreign exchange contracts, maximum		12 months
Unrealized losses in AOCI at time of de-designation	$ (2,714.3)	$ (2,714.3)	$ (2,709.5)	$ (2,660.0)	$ (2,842.3)	$ (2,855.0)	$ (2,921.9)
Foreign currency cash flow hedge gains estimated to be reclassified into earnings during next 12 months	1.2	1.2
Interest rate swap cash flow hedge loss estimated to be reclassified into earnings during next 12 months	44.4	44.4
Interest rate swaps
Derivative [Line Items]
Interest rate swaps, modification, notional amount	$ 200.0	$ 1,400.0
Fixed pay rate	2.25%	2.25%		2.87%
Notational amount, de-designated		$ 1,400.0
Gross amount of swaps in an asset position subject to master netting arrangement	$ 161.3	161.3
Gross amount of swaps in an liability position subject to master netting arrangement	276.4	276.4
Net liability of swaps subject to master netting arrangement	$ 115.1	$ 115.1
Minimum | Interest rate swaps
Derivative [Line Items]
Extended maturity		2 years
Maximum | Interest rate swaps
Derivative [Line Items]
Extended maturity		5 years
Not Designated as Hedging Instrument | Interest rate swaps
Derivative [Line Items]
Notational amount entered into during period		$ 1,400.0
Designated as Hedging Instrument | Interest rate swaps
Derivative [Line Items]
Notational amount entered into during period		$ 1,400.0
Accumulated Gain (Loss), Net, Cash Flow Hedge Discontinued, Including Noncontrolling Interest | Interest rate swaps
Derivative [Line Items]
Unrealized losses in AOCI at time of de-designation				$ 163.0