INVESTMENTS - Investment Exposures Individually Exceeded 10% of Shareholders' Equity (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Mar. 31, 2024	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Credit Rating	[1]	A+	A+
Investment, Type [Extensible Enumeration]		Japan National Government [Member]	Japan National Government [Member]	[1]
Amortized Cost	[1]	$ 36,641	$ 39,151
Fair Value	[1]	$ 37,170	$ 40,222

[1] Japan Government Bonds (JGBs) or JGB-backed securities