INVESTMENTS - AFS Fixed Maturity Securities (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Cost or amortized cost	$ 73,600,788	$ 69,519,496
Allowance for Credit Losses	(128,332)	(88,133)	$ (120,895)
Gross unrealized gains	73,312	413,373
Gross unrealized losses	(11,606,239)	(973,850)
Fair value	61,939,529	68,870,886
Allowance for credit losses at acquisition	(29,900)	(46,400)
U.S. government and agencies
Debt Securities, Available-for-sale [Line Items]
Cost or amortized cost	438,931	785,144
Allowance for Credit Losses	0	0
Gross unrealized gains	304	4,171
Gross unrealized losses	(72,494)	(4,768)
Fair value	366,741	784,547
U.S. state, municipal and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Cost or amortized cost	5,638,252	5,122,651
Allowance for Credit Losses	0	0
Gross unrealized gains	6,582	42,286
Gross unrealized losses	(1,233,874)	(55,240)
Fair value	4,410,960	5,109,697
Corporate
Debt Securities, Available-for-sale [Line Items]
Cost or amortized cost	44,253,062	41,433,757
Allowance for Credit Losses	(1,298)	(3,238)	$ 0
Gross unrealized gains	49,509	190,516
Gross unrealized losses	(7,984,341)	(688,648)
Fair value	36,316,932	40,932,387
Residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Cost or amortized cost	7,307,526	7,703,030
Allowance for Credit Losses	(100,554)	(50,975)
Gross unrealized gains	12,052	126,662
Gross unrealized losses	(834,212)	(113,359)
Fair value	6,384,812	7,665,358
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Cost or amortized cost	7,269,662	5,952,656
Allowance for Credit Losses	(14,490)	(282)
Gross unrealized gains	36	16,332
Gross unrealized losses	(834,735)	(56,523)
Fair value	6,420,473	5,912,183
Collateralized bond obligations
Debt Securities, Available-for-sale [Line Items]
Cost or amortized cost	3,051,850	3,111,620
Allowance for Credit Losses	(426)	(22,160)
Gross unrealized gains	0	6,862
Gross unrealized losses	(217,773)	(27,466)
Fair value	2,833,651	3,068,856
CLOs
Debt Securities, Available-for-sale [Line Items]
Cost or amortized cost	2,726,888	2,985,098
Allowance for Credit Losses	(6,165)	(639)
Gross unrealized gains	127	6,554
Gross unrealized losses	(200,160)	(5,776)
Fair value	2,520,690	2,985,237
Asset-Backed Securities
Debt Securities, Available-for-sale [Line Items]
Cost or amortized cost	2,914,617	2,425,540
Allowance for Credit Losses	(5,399)	(10,839)
Gross unrealized gains	4,702	19,990
Gross unrealized losses	(228,650)	(22,070)
Fair value	$ 2,685,270	$ 2,412,621

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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