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Debt - Principal Terms of Senior and Junior Subordinated Notes (Details) $ in Millions | 12 Months Ended
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Dec. 31, 2020 USD ($)
Senior notes | 2024 Senior Notes |
Debt Instrument [Line Items] |
Principal Amount at Maturity | $ 400.0
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] |
Principal Amount at Maturity | $ 350.0
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] |
Principal Amount at Maturity | $ 350.0
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] |
Principal Amount at Maturity | $ 300.0
Stated coupon | 5.875%
Junior subordinated notes | 2059 Junior Subordinated Notes | On or after March 30. 2024 |
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] |
Principal Amount at Maturity | $ 275.0
Stated coupon | 4.75%
Junior subordinated notes | 2060 Junior Subordinated Notes | On or after March 30. 2024 |
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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