Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Fixed income securities, amortized cost	$ 2,807	$ 3,187
Other Investments	$ 595	$ 478
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred Stock, Shares Outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	130,000,000	130,000,000
Common stock, shares issued	45,865,081	45,571,743
Common Stock, Shares, Outstanding	45,809,139
Treasury stock, shares	55,942	16,343
Fixed Income Securities [Member]
Fixed income securities, amortized cost	$ 2,175	$ 2,450
Equity investments in pooled funds [Member]
Other Investments	543	432
Other Investment Not Readily Marketable, Fair Value	544	432
Collateral Pledged [Member] \| Fixed Income Securities [Member]
Fixed income securities, amortized cost	15	0
Parent Company [Member]
Fixed income securities, amortized cost	76	71
Other Investments	54	46
Short-term Investments [Member]
Fixed income securities, amortized cost	492	653
Short-term Investments [Member] \| Fixed Income Securities [Member]
Fixed income securities, amortized cost		653
Short-term Investments [Member] \| Parent Company [Member]
Fixed income securities, amortized cost	$ 229	$ 318

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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