SCHEDULE II - CONDENSED FINANCIAL INFORMATION OF REGISTRANT - Condensed Statements 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 income	$ 762,994	$ 712,949	$ 865,349
Adjustments to reconcile net income to net cash provided by operating activities:
Deferred tax (benefit) expense	1,805	1,550	(5,235)
Loss on debt extinguishment	0	0	40,199
Change in certain assets and liabilities:
Accrued investment income	(2,290)	(3,596)	(3,276)
Net cash provided by operating activities	725,032	712,962	650,012
Cash flows from investing activities:
Purchases of investments	(1,555,624)	(1,469,540)	(674,406)
Proceeds from sales of investments	45,087	376,598	399,661
Net cash (used in) provided by investing activities	(142,005)	(179,190)	410,485
Cash flows from financing activities:
Conversion / purchase of convertible junior subordinated debentures	0	(28,637)	(89,118)
Redemption of 5.75% senior notes	0	0	(242,296)
Cash portion of loss on debt extinguishment	0	0	(39,514)
Repurchase of common stock	(569,478)	(337,182)	(385,573)
Dividends paid	(130,500)	(122,965)	(110,947)
Payment of withholding taxes related to share-based compensation net share settlement	(19,066)	(7,257)	(10,094)
Net cash used in financing activities	(719,044)	(496,041)	(1,032,542)
Net (decrease) increase in cash and cash equivalents and restricted cash and cash equivalents	(136,017)	37,731	27,955
Cash and cash equivalents and restricted cash and cash equivalents at beginning of year	370,644	332,913	304,958
Cash and cash equivalents and restricted cash and cash equivalents at end of year	234,627	370,644	332,913
Parent Company
Cash flows from operating activities:
Net income	762,994	712,949	865,349
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in net income of subsidiaries	(752,882)	(719,599)	(930,979)
Dividends received from subsidiaries	526,879	326,013	626,695
Deferred tax (benefit) expense	36,798	86,219	119,588
Loss on debt extinguishment	0	0	38,870
Other	19,298	26,726	33,619
Change in certain assets and liabilities:
Accounts receivable - affiliates	348	(1,996)	1,266
Income taxes receivable	(5,683)	45,913	(43,123)
Accrued investment income	1,007	(499)	931
Accrued interest	0	349	(7,230)
Net cash provided by operating activities	588,759	476,075	704,986
Cash flows from investing activities:
Return of capital from subsidiaries	40,000	0	0
Purchases of investments	(514,482)	(566,795)	(1,457)
Proceeds from sales of investments	546,111	555,957	287,924
Net cash (used in) provided by investing activities	71,629	(10,838)	286,467
Cash flows from financing activities:
Conversion / purchase of convertible junior subordinated debentures	0	(28,637)	(89,118)
Redemption of 5.75% senior notes	0	0	(242,296)
Cash portion of loss on debt extinguishment	0	0	(38,185)
Repurchase of common stock	(569,478)	(337,182)	(385,573)
Dividends paid	(130,500)	(122,965)	(110,947)
Payment of withholding taxes related to share-based compensation net share settlement	(19,066)	(7,257)	(10,094)
Net cash used in financing activities	(719,044)	(496,041)	(876,213)
Net (decrease) increase in cash and cash equivalents and restricted cash and cash equivalents	(58,656)	(30,804)	115,240
Cash and cash equivalents and restricted cash and cash equivalents at beginning of year	208,600	239,404	124,164
Cash and cash equivalents and restricted cash and cash equivalents at end of year	$ 149,944	$ 208,600	$ 239,404