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Debt - Schedule of Principal Terms of Senior and Junior Subordinated Notes (Details)	6 Months Ended
	Jun. 30, 2021 USD ($)
Senior notes | 2024 Senior Notes
Debt Instrument [Line Items]
Par value	$ 400,000,000.0
Stated coupon	4.25%
Redemption price percentage	100.00%
Senior notes | 2024 Senior Notes | Treasury Rate
Debt Instrument [Line Items]
Applicable basis spread over redemption price percentage	0.25%
Senior notes | 2025 Senior Notes
Debt Instrument [Line Items]
Par value	$ 350,000,000.0
Stated coupon	3.50%
Redemption price percentage	100.00%
Senior notes | 2025 Senior Notes | Treasury Rate
Debt Instrument [Line Items]
Applicable basis spread over redemption price percentage	0.25%
Senior notes | 2030 Senior Notes
Debt Instrument [Line Items]
Par value	$ 350,000,000.0
Stated coupon	3.30%
Redemption price percentage	100.00%
Senior notes | 2030 Senior Notes | Treasury Rate
Debt Instrument [Line Items]
Applicable basis spread over redemption price percentage	0.40%
Junior subordinated notes | 2059 Junior Subordinated Notes
Debt Instrument [Line Items]
Par value	$ 300,000,000.0
Stated coupon	5.875%
Junior subordinated notes | 2059 Junior Subordinated Notes | On or after March 30. 2024 (after September 30, 2025 - 2060 Junior Subordinated Notes)
Debt Instrument [Line Items]
Redemption price percentage	100.00%
Junior subordinated notes | 2059 Junior Subordinated Notes | If changes in tax laws and interpretations occur
Debt Instrument [Line Items]
Redemption price percentage	100.00%
Junior subordinated notes | 2059 Junior Subordinated Notes | If a rating agency makes certain changes relating to the equity credit criteria for securities
Debt Instrument [Line Items]
Redemption price percentage	102.00%
Junior subordinated notes | 2060 Junior Subordinated Notes
Debt Instrument [Line Items]
Par value	$ 275,000,000.0
Stated coupon	4.75%
Junior subordinated notes | 2060 Junior Subordinated Notes | On or after March 30. 2024 (after September 30, 2025 - 2060 Junior Subordinated Notes)
Debt Instrument [Line Items]
Redemption price percentage	100.00%
Junior subordinated notes | 2060 Junior Subordinated Notes | If changes in tax laws and interpretations occur
Debt Instrument [Line Items]
Redemption price percentage	100.00%
Junior subordinated notes | 2060 Junior Subordinated Notes | If a rating agency makes certain changes relating to the equity credit criteria for securities
Debt Instrument [Line Items]
Redemption price percentage	102.00%

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Debt Instrument, Make Whole Premium, Discount Rate, Basis Spread on Variable Rate

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Face (par) amount of debt instrument at time of issuance.

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Contractual interest rate for funds borrowed, under the debt agreement.

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