Financial Instruments and Fair Value Measurements - Derivative Financial Instruments (Details) - Cash flow hedge $ in Millions	Jun. 30, 2020 USD ($) derivative	Feb. 29, 2020 USD ($) derivative	Dec. 31, 2019 USD ($)
Designated as hedging instrument
Derivative [Line Items]
Notional Amount	$ 923.3		$ 673.4
Fair Value - asset (liability)	(54.9)		(26.3)
Interest rate swap, maturity Sep 2021 | Designated as hedging instrument
Derivative [Line Items]
Notional Amount	$ 6.9		7.0
Strike (percent)	6.03%
Fair Value - asset (liability)	$ (0.3)		(0.2)
Interest rate swap, maturity Jun 2020 | Designated as hedging instrument
Derivative [Line Items]
Notional Amount	$ 0.0		250.0
Strike (percent)	1.72%
Fair Value - asset (liability)	$ 0.0		(0.1)
Interest rate swap, maturity Mar 2024 | Designated as hedging instrument
Derivative [Line Items]
Notional Amount	$ 250.0		250.0
Strike (percent)	3.04%
Fair Value - asset (liability)	$ (25.9)		(14.7)
Cross-currency swap, maturity May 2034 1 | Designated as hedging instrument
Derivative [Line Items]
Notional Amount	41.6		41.6
Fair Value - asset (liability)	$ 5.0		(2.6)
Cross-currency swap, maturity May 2034 1 | Designated as hedging instrument | GBP | Minimum
Derivative [Line Items]
Strike (percent)	4.82%
Cross-currency swap, maturity May 2034 1 | Designated as hedging instrument | GBP | Maximum
Derivative [Line Items]
Strike (percent)	10.96%
Cross-currency swap, maturity May 2034 1 | Designated as hedging instrument | USD
Derivative [Line Items]
Strike (percent)	9.80%
Cross-currency swap, maturity May 2034 2 | Designated as hedging instrument
Derivative [Line Items]
Notional Amount	$ 41.6		41.6
Fair Value - asset (liability)	$ 4.9		(2.6)
Cross-currency swap, maturity May 2034 2 | Designated as hedging instrument | GBP | Minimum
Derivative [Line Items]
Strike (percent)	4.82%
Cross-currency swap, maturity May 2034 2 | Designated as hedging instrument | GBP | Maximum
Derivative [Line Items]
Strike (percent)	10.96%
Cross-currency swap, maturity May 2034 2 | Designated as hedging instrument | USD
Derivative [Line Items]
Strike (percent)	9.803%
Cross-currency swap, maturity May 2034 3 | Designated as hedging instrument
Derivative [Line Items]
Notional Amount	$ 41.6		41.6
Fair Value - asset (liability)	$ 4.6		(2.9)
Cross-currency swap, maturity May 2034 3 | Designated as hedging instrument | GBP | Minimum
Derivative [Line Items]
Strike (percent)	4.82%
Cross-currency swap, maturity May 2034 3 | Designated as hedging instrument | GBP | Maximum
Derivative [Line Items]
Strike (percent)	10.96%
Cross-currency swap, maturity May 2034 3 | Designated as hedging instrument | USD
Derivative [Line Items]
Strike (percent)	9.745%
Cross-currency swap, maturity May 2034 4 | Designated as hedging instrument
Derivative [Line Items]
Notional Amount	$ 41.6		41.6
Fair Value - asset (liability)	$ 4.5		(3.2)
Cross-currency swap, maturity May 2034 4 | Designated as hedging instrument | GBP | Minimum
Derivative [Line Items]
Strike (percent)	4.82%
Cross-currency swap, maturity May 2034 4 | Designated as hedging instrument | GBP | Maximum
Derivative [Line Items]
Strike (percent)	10.96%
Cross-currency swap, maturity May 2034 4 | Designated as hedging instrument | USD
Derivative [Line Items]
Strike (percent)	9.755%
Forward-starting swap, maturity Jun 2033 1 | Designated as hedging instrument
Derivative [Line Items]
Notional Amount	$ 75.0		0.0
Strike (percent)	2.02%
Fair Value - asset (liability)	$ (7.9)		0.0
Forward-starting swap, maturity Nov 2032 1 | Designated as hedging instrument
Derivative [Line Items]
Notional Amount	$ 75.0		0.0
Strike (percent)	1.94%
Fair Value - asset (liability)	$ (7.8)		0.0
Forward-starting swap, maturity Nov 2032 2 | Designated as hedging instrument
Derivative [Line Items]
Notional Amount	$ 25.0		0.0
Strike (percent)	1.67%
Fair Value - asset (liability)	$ (2.0)		0.0
Forward-starting swap, maturity Jun 2033 2 | Designated as hedging instrument
Derivative [Line Items]
Notional Amount	$ 125.0		0.0
Strike (percent)	1.75%
Fair Value - asset (liability)	$ (9.9)		0.0
Forward-starting swap, hybrid debt, maturity Nov 2032 3 | Designated as hedging instrument
Derivative [Line Items]
Notional Amount	$ 125.0		0.0
Strike (percent)	1.88%
Fair Value - asset (liability)	$ (12.3)		0.0
Forward-starting swap, hybrid debt, maturity Jun 2033 3 | Designated as hedging instrument
Derivative [Line Items]
Notional Amount	$ 75.0		0.0
Strike (percent)	2.00%
Fair Value - asset (liability)	$ (7.8)		$ 0.0
Treasury rate locks
Derivative [Line Items]
Notional Amount		$ 500.0
Number of derivative instruments | derivative		5
Forward-Starting Swap [Member]
Derivative [Line Items]
Notional Amount	$ 500.0
Number of derivative instruments | derivative	6