Schedule II - Financial Information of Registrant - Parent Company Statement of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Cash flows from operating activities
Net cash provided by (used in) operating activities	$ (663,572)	$ 529,434	$ 388,298
Proceeds from sales of:
Trading securities	0	9,123	8,868
Proceeds from redemptions of:
Available for sale securities	903,395	498,081	789,929
Trading securities	17,081	1,707	102,121
Purchases of:
Available for sale securities	(1,344,925)	(933,264)	(1,414,966)
Equity securities	(23,425)	(8,334)	(24,637)
Sales, redemptions and (purchases) of:
Short-term investments, net	153,243	(251,662)	150,694
Other assets, net	1,115	(45)	(6,887)
Net cash provided by (used in) investing activities	327,746	(300,842)	(5,175)
Cash flows from financing activities
Dividends and dividend equivalents paid	(151,961)	(145,908)	(135,437)
Issuance of common stock	928	1,755	1,341
Repurchases of common stock	(225,059)	(133,314)	(400,195)
Issuance of senior notes	616,745	0	0
Redemption of senior notes	(977,079)	0	0
Credit facility commitment fees paid	(812)	(904)	(814)
Proceeds (repayments) related to cash collateral for loaned securities, net	(23,641)	49,629	51,083
Net cash provided by (used in) financing activities	357,233	(265,087)	(479,183)
Increase (decrease) in cash and restricted cash	21,407	(36,495)	(96,060)
Cash and restricted cash, beginning of period	20,065	56,560	152,620
Cash and restricted cash, end of period	41,472	20,065	56,560
Parent Company
Cash flows from operating activities
Net cash provided by (used in) operating activities	246,885	194,607	(71)
Proceeds from sales of:
Available for sale securities	18,423	129,650	56,934
Trading securities	0	0	8,868
Equity securities	38,375	60,755	0
Proceeds from redemptions of:
Available for sale securities	320,026	168,639	194,859
Trading securities	23	0	0
Purchases of:
Available for sale securities	(63,733)	(84,313)	(29,039)
Equity securities	(18,166)	(3,690)	(2,500)
Sales, redemptions and (purchases) of:
Short-term investments, net	339,819	(135,657)	188,149
Other assets, net	(158)	(10,664)	(3,851)
Capital distributions from subsidiaries	500	7,000	32,512
Capital contributions to subsidiaries	(84,000)	(49,750)	(8,000)
Net cash provided by (used in) investing activities	551,109	81,970	437,932
Cash flows from financing activities
Dividends and dividend equivalents paid	(151,961)	(145,908)	(135,437)
Issuance of common stock	928	1,755	1,341
Repurchases of common stock	(225,059)	(133,314)	(400,195)
Issuance of senior notes	616,745	0	0
Redemption of senior notes	(977,079)	0	0
Credit facility commitment fees paid	(812)	(904)	(814)
Proceeds (repayments) related to cash collateral for loaned securities, net	(57,174)	2,122	60,270
Net cash provided by (used in) financing activities	(794,412)	(276,249)	(474,835)
Increase (decrease) in cash and restricted cash	3,582	328	(36,974)
Cash and restricted cash, beginning of period	2,200	1,872	38,846
Cash and restricted cash, end of period	5,782	2,200	1,872
Cash distributions received from consolidated subsidiaries	243,000	191,000	50,000
Dividends received from consolidated subsidiaries	$ 432,000	$ 218,000	$ 888,000

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