Debt - Schedule of Principal Terms of Senior and Junior Subordinated Notes (Details)	Sep. 30, 2021 USD ($)
Senior notes | 2024 Senior Notes
Debt Instrument [Line Items]
Par value	$ 400,000,000.0
Stated coupon	4.25%
Senior notes | 2025 Senior Notes
Debt Instrument [Line Items]
Par value	$ 350,000,000.0
Stated coupon	3.50%
Senior notes | 2030 Senior Notes
Debt Instrument [Line Items]
Par value	$ 350,000,000.0
Stated coupon	3.30%
Junior subordinated notes | 2059 Junior Subordinated Notes
Debt Instrument [Line Items]
Par value	$ 300,000,000.0
Stated coupon	5.875%
Junior subordinated notes | 2060 Junior Subordinated Notes
Debt Instrument [Line Items]
Par value	$ 275,000,000.0
Stated coupon	4.75%
Junior subordinated notes | 2061 Junior Subordinated Notes
Debt Instrument [Line Items]
Par value	$ 200,000,000.0
Stated coupon	4.20%