Derivative Instruments - Notional Amount of Derivatives and Other Financial Instruments (Details) £ in Thousands, $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($)	Dec. 31, 2020 CAD ($)	Dec. 31, 2020 GBP (£)	Dec. 31, 2020 USD ($)	Dec. 31, 2020 CAD ($)	Dec. 31, 2020 GBP (£)
Designated as Hedging Instrument | Net Investment Hedging | Denominated in Canadian Dollars
Derivatives, Fair Value [Line Items]
Derivative asset	$ 675,000				$ 625,000
Notional amount of non-derivative instruments	250,000	$ 250,000
Designated as Hedging Instrument | Net Investment Hedging | Denominated in Pound Sterling
Derivatives, Fair Value [Line Items]
Derivative asset	1,904,708					£ 1,340,708
Notional amount of non-derivative instruments	1,050,000		£ 1,050,000
Designated as Hedging Instrument | Cash Flow Hedging | Denominated in U.S. Dollars
Derivatives, Fair Value [Line Items]
Derivative asset	25,000			$ 450,000
Not Designated as Hedging Instrument | Denominated in Canadian Dollars | Short
Derivatives, Fair Value [Line Items]
Derivative asset	80,000				$ 80,000
Not Designated as Hedging Instrument | Denominated in U.S. Dollars
Derivatives, Fair Value [Line Items]
Derivative asset	$ 26,137			$ 26,137