Investments - Consolidated Investments (Details) - USD ($) $ in Millions	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Available-for-sale securities
Amortized Cost	$ 25,178.0		$ 2,029.0
Allowance for Expected Credit Losses	(22.0)	$ (28.0)	0.0
Gross Unrealized Gains	1,316.0		67.0
Gross Unrealized Losses	(62.0)		(6.0)
Fair value	26,410.0		2,090.0
Asset-backed securities
Available-for-sale securities
Amortized Cost	5,527.0
Allowance for Expected Credit Losses	0.0	(2.0)	0.0
Gross Unrealized Gains	221.0
Gross Unrealized Losses	(8.0)
Fair value	5,739.0
Commercial mortgage-backed securities
Available-for-sale securities
Amortized Cost	2,501.0		22.0
Allowance for Expected Credit Losses	0.0
Gross Unrealized Gains	275.0		0.0
Gross Unrealized Losses	(4.0)		0.0
Fair value	2,772.0		22.0
Corporates
Available-for-sale securities
Amortized Cost	13,340.0		1,510.0
Allowance for Expected Credit Losses	(18.0)	(21.0)	0.0
Gross Unrealized Gains	687.0		49.0
Gross Unrealized Losses	(45.0)		(3.0)
Fair value	13,965.0		1,556.0
Hybrids
Available-for-sale securities
Amortized Cost	951.0		26.0
Allowance for Expected Credit Losses	0.0	0.0	0.0
Gross Unrealized Gains	45.0		5.0
Gross Unrealized Losses	(3.0)		0.0
Fair value	993.0		31.0
Municipals
Available-for-sale securities
Amortized Cost	1,408.0		90.0
Allowance for Expected Credit Losses	0.0
Gross Unrealized Gains	59.0		3.0
Gross Unrealized Losses	(1.0)		0.0
Fair value	1,466.0		93.0
Residential mortgage-backed securities
Available-for-sale securities
Amortized Cost	878.0		38.0
Allowance for Expected Credit Losses	(4.0)	$ (5.0)	0.0
Gross Unrealized Gains	9.0		2.0
Gross Unrealized Losses	(1.0)		0.0
Fair value	882.0		40.0
U.S. Government
Available-for-sale securities
Amortized Cost	394.0		282.0
Allowance for Expected Credit Losses	0.0
Gross Unrealized Gains	11.0		7.0
Gross Unrealized Losses	0.0		(1.0)
Fair value	405.0		288.0
Foreign Governments
Available-for-sale securities
Amortized Cost	179.0		61.0
Allowance for Expected Credit Losses	0.0
Gross Unrealized Gains	9.0		1.0
Gross Unrealized Losses	0.0		(2.0)
Fair value	$ 188.0		$ 60.0

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on 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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