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Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Fixed income securities, amortized cost	$ 2,140
Short-term investments, amortized cost	415	$ 492
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Uncollectable premium receivables	9	17
Reinsurance Recoverable, Allowance for Credit Loss	$ 0	$ 0
Preferred stock, par value	$ 0.01
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred Stock, Shares Outstanding	0	0
Common stock, shares authorized	130,000,000	130,000,000
Common stock, shares issued	46,477,068	45,865,081
Common Stock, Shares, Outstanding	46,304,139
Treasury stock, shares	172,929	55,942
Fixed Income Securities [Member]
Fixed income securities, amortized cost	$ 1,605	$ 2,175
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Equity investments in pooled funds [Member]
Other Investment Not Readily Marketable, Fair Value	683	544
Collateral Pledged [Member]
Short-term investments, amortized cost	105	125
Collateral Pledged [Member] | Fixed Income Securities [Member]
Fixed income securities, amortized cost	15	15
Short-term Investments [Member]
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Short-term Investments [Member] | Collateral Pledged [Member] | Fixed Income Securities [Member]
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Variable Interest Entity, Primary Beneficiary [Member]
Long-term Debt	4,056	4,324
Parent Company [Member]
Fixed income securities, amortized cost	130	76
Debt Securities, Available-for-sale, Allowance for Credit Loss	3	2
Parent Company [Member] | Short-term Investments [Member]
Fixed income securities, amortized cost	$ 124	$ 229

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