INVESTMENTS - Credit Quality (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Financing Receivable, before Allowance for Credit Loss [Abstract]
Total	$ 549	$ 296
Total	549	296
Non-accruing Loans	0	0
Non-accruing Loans with No Allowance	0	0
Interest Income on Non-accruing Loans	0	0
Past Due
Financing Receivable, before Allowance for Credit Loss [Abstract]
Total	0	0
30-59 Days
Financing Receivable, before Allowance for Credit Loss [Abstract]
Total	0	0
60-89 Days
Financing Receivable, before Allowance for Credit Loss [Abstract]
Total	0	0
90 Days or More
Financing Receivable, before Allowance for Credit Loss [Abstract]
Total	0	0
Current
Financing Receivable, before Allowance for Credit Loss [Abstract]
Total	549	296
Commercial:
Financing Receivable, before Allowance for Credit Loss [Abstract]
Current fiscal year	122	279
Fiscal year before current fiscal year	279	0
Two years before current fiscal year	0	0
Three years before current fiscal year	0	0
Four years before current fiscal year	0	0
Prior	17	17
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	418	296
Total	418	296
Non-accruing Loans	0	0
Non-accruing Loans with No Allowance	0	0
Interest Income on Non-accruing Loans	0	0
Commercial: | Past Due
Financing Receivable, before Allowance for Credit Loss [Abstract]
Total	0	0
Commercial: | 30-59 Days
Financing Receivable, before Allowance for Credit Loss [Abstract]
Total	0	0
Commercial: | 60-89 Days
Financing Receivable, before Allowance for Credit Loss [Abstract]
Total	0	0
Commercial: | 90 Days or More
Financing Receivable, before Allowance for Credit Loss [Abstract]
Total	0	0
Commercial: | Current
Financing Receivable, before Allowance for Credit Loss [Abstract]
Total	418	296
Commercial: | Greater than 2.0x
Financing Receivable, before Allowance for Credit Loss [Abstract]
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Two years before current fiscal year	0	0
Three years before current fiscal year	0	0
Four years before current fiscal year	0	0
Prior	17	17
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	17	17
Commercial: | 1.8x to 2.0x
Financing Receivable, before Allowance for Credit Loss [Abstract]
Current fiscal year	40	0
Fiscal year before current fiscal year	0	0
Two years before current fiscal year	0	0
Three years before current fiscal year	0	0
Four years before current fiscal year	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	40	0
Commercial: | 1.5x to 1.8x
Financing Receivable, before Allowance for Credit Loss [Abstract]
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Two years before current fiscal year	0	0
Three years before current fiscal year	0	0
Four years before current fiscal year	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	0	0
Commercial: | 1.2x to 1.5x
Financing Receivable, before Allowance for Credit Loss [Abstract]
Current fiscal year	82	221
Fiscal year before current fiscal year	221	0
Two years before current fiscal year	0	0
Three years before current fiscal year	0	0
Four years before current fiscal year	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	303	221
Commercial: | 1.0x to 1.2x
Financing Receivable, before Allowance for Credit Loss [Abstract]
Current fiscal year	0	58
Fiscal year before current fiscal year	58	0
Two years before current fiscal year	0	0
Three years before current fiscal year	0	0
Four years before current fiscal year	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	58	58
Commercial: | Less than 1.0x
Financing Receivable, before Allowance for Credit Loss [Abstract]
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Two years before current fiscal year	0	0
Three years before current fiscal year	0	0
Four years before current fiscal year	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	0	0
Commercial: | 0% - 50%
Financing Receivable, before Allowance for Credit Loss [Abstract]
Current fiscal year	0	58
Fiscal year before current fiscal year	58	0
Two years before current fiscal year	0	0
Three years before current fiscal year	0	0
Four years before current fiscal year	0	0
Prior	17	17
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	75	75
Commercial: | 50% - 70%
Financing Receivable, before Allowance for Credit Loss [Abstract]
Current fiscal year	122	221
Fiscal year before current fiscal year	221	0
Two years before current fiscal year	0	0
Three years before current fiscal year	0	0
Four years before current fiscal year	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	343	221
Commercial: | 70% - 90%
Financing Receivable, before Allowance for Credit Loss [Abstract]
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Two years before current fiscal year	0	0
Three years before current fiscal year	0	0
Four years before current fiscal year	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	0	0
Commercial: | 90% plus
Financing Receivable, before Allowance for Credit Loss [Abstract]
Current fiscal year	0	0
Fiscal year before current fiscal year	0	0
Two years before current fiscal year	0	0
Three years before current fiscal year	0	0
Four years before current fiscal year	0	0
Prior	0	0
Revolving Loans Amortized Cost Basis	0	0
Revolving Loans Converted to Term Loans Amortized Cost Basis	0	0
Total	0	0
Residential
Financing Receivable, before Allowance for Credit Loss [Abstract]
Current fiscal year	0
Fiscal year before current fiscal year	96
Two years before current fiscal year	18
Three years before current fiscal year	16
Four years before current fiscal year	1
Prior	0
Total	131	0
Total	131	0
Non-accruing Loans	0	0
Non-accruing Loans with No Allowance	0	0
Interest Income on Non-accruing Loans	0	0
Residential | Past Due
Financing Receivable, before Allowance for Credit Loss [Abstract]
Total	0	0
Residential | 30-59 Days
Financing Receivable, before Allowance for Credit Loss [Abstract]
Total	0	0
Residential | 60-89 Days
Financing Receivable, before Allowance for Credit Loss [Abstract]
Total	0	0
Residential | 90 Days or More
Financing Receivable, before Allowance for Credit Loss [Abstract]
Total	0	0
Residential | Current
Financing Receivable, before Allowance for Credit Loss [Abstract]
Total	$ 131	$ 0