Derivative Instruments - Notional Amount of Derivatives and Other Financial Instruments (Details) £ in Thousands, $ in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2022 CAD ($)	Mar. 31, 2022 GBP (£)	Jun. 30, 2021 CAD ($)	Jun. 30, 2021 GBP (£)	Mar. 31, 2022 GBP (£)	Mar. 31, 2022 USD ($)	Dec. 31, 2021 CAD ($)	Dec. 31, 2021 GBP (£)	Dec. 31, 2021 USD ($)
Denominated in Canadian Dollars | Designated as Hedging Instrument | Net Investment Hedging
Derivatives, Fair Value [Line Items]
Derivative asset	$ 1,075,000						$ 675,000
Net investment hedges	250,000		$ 250,000
Denominated in Canadian Dollars | Derivative Instruments Not Designated | Purchase Contracts
Derivatives, Fair Value [Line Items]
Derivative asset	$ 80,000						$ 80,000
Denominated in Pound Sterling | Designated as Hedging Instrument | Net Investment Hedging
Derivatives, Fair Value [Line Items]
Derivative asset | £					£ 1,890,708			£ 1,904,708
Net investment hedges | £		£ 1,050,000		£ 1,050,000
Denominated in U.S Dollars | Designated as Hedging Instrument | Cash Flow Hedging
Derivatives, Fair Value [Line Items]
Derivative asset						$ 25,000			$ 25,000
Denominated in U.S Dollars | Designated as Hedging Instrument | Fair Value Hedging
Derivatives, Fair Value [Line Items]
Derivative asset						550,000			0
Denominated in U.S Dollars | Derivative Instruments Not Designated
Derivatives, Fair Value [Line Items]
Derivative asset						$ 26,137			$ 26,137