Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Cash flows from operating activities
Net income	$ 456,149	$ 460,426
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Net (gains) losses on investments and other financial instruments	1,823	3,206
Net (gains) losses on consolidated VIE assets and liabilities	(265)	0
Purchases of residential mortgage loans held for sale	(1,143,220)	(187,163)
Proceeds from sales of residential mortgage loans held for sale	273,848	36,677
Principal payments from residential mortgage loans held for sale	19,989	13,870
Loss on extinguishment of debt	4,275	0
Amortization of other acquired intangible assets	0	4,112
Depreciation, other amortization, and other impairments, net	53,025	43,476
Deferred income tax provision	122,056	123,565
Change in:
Accrued investment income	(5,877)	(5,530)
Accounts and notes receivable	(11,697)	(24,888)
Reinsurance recoverable	(8,106)	1,484
Deferred policy acquisition costs	288	(357)
Prepaid federal income tax	(120,016)	(100,452)
Other assets	11,115	37,841
Unearned premiums	(27,389)	(35,078)
Reserve for losses and LAE	(6,923)	(59,275)
Reinsurance funds withheld	8,246	4,047
Other liabilities	(21,478)	(51,485)
Net cash provided by (used in) operating activities	(394,157)	264,476
Proceeds from sales of:
Fixed-maturities available for sale	391,612	266,206
Trading securities	0	9,123
Equity securities	28,503	46,136
Proceeds from redemptions of:
Fixed-maturities available for sale	648,451	384,262
Trading securities	16,929	1,538
Purchases of:
Fixed-maturities available for sale	(1,019,843)	(796,087)
Equity securities	(21,976)	(5,711)
Sales, redemptions and (purchases) of:
Short-term investments, net	241,802	(77,572)
Other assets and other invested assets, net	1,274	(2,945)
Principal payments from securitized residential mortgage loans held for investment	8,508	0
Additions to property and equipment	(2,831)	(14,395)
Net cash provided by (used in) investing activities	292,429	(189,445)
Cash flows from financing activities
Dividends and dividend equivalents paid	(115,227)	(111,029)
Issuance of common stock	928	1,533
Repurchases of common stock	(149,043)	(70,028)
Issuance of senior notes	616,745	0
Redemption of senior notes	(977,079)	0
Issuance of securitized nonrecourse debt	344,514	0
Repayments of securitized nonrecourse debt	(8,508)	0
Proceeds (repayments) related to cash collateral for loaned securities, net	(32,459)	19,462
Proceeds from secured borrowings	1,654,037	389,408
Repayments of secured borrowings	(1,221,597)	(303,477)
Credit facility commitment fees paid	(573)	(666)
Net cash provided by (used in) financing activities	111,738	(74,797)
Increase (decrease) in cash and restricted cash	10,010	234
Cash and restricted cash, beginning of period	20,065	56,560
Cash and restricted cash, end of period	30,075	56,794
Noncash Investing and Financing Items [Abstract]
Transfer from residential mortgage loans held for sale to securitized residential mortgage loans held for investment	350,875	0
Retention of mortgage servicing rights from residential mortgage loan sales	2,189	0
Operating lease right-of-use assets obtained in exchange for operating lease liabilities	$ 1,242	$ 0