Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax asset:
Loss reserve discounting	$ 230,956	$ 192,181
Unearned premiums	200,938	180,326
Unrealized investment losses	126,693	228,456
Net operating losses & foreign tax credits	59,154	58,182
Other-than-temporary impairments	12,691	5,935
Employee compensation plans	68,062	63,313
Other	78,025	72,536
Gross deferred tax asset	776,519	800,929
Less valuation allowance	(36,283)	(47,166)
Deferred tax asset	740,236	753,763
Deferred tax liability:
Amortization of intangibles	15,205	13,973
Loss reserve discounting - transition rule	9,894	14,843
Deferred policy acquisition costs	176,281	157,055
Property, furniture and equipment	43,501	45,887
Investment funds	161,867	125,525
Other	66,525	67,479
Deferred tax liability	473,273	424,762
Net deferred tax asset	266,963	329,001
Operating Loss Carryforwards [Line Items]
Income taxes receivable		5,000
Current federal income taxes	46,000
Valuation allowance	36,000	$ 47,000
Foreign Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, subject to expire	$ 220,000