Schedule I - Financial Information of the Registrant (Parent Company) - Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Assets
Cash and cash equivalents	$ 233,365	$ 248,367
Property and equipment, at cost:
Accumulated depreciation	(173,799)	(153,474)
Total property and equipment, at cost	82,335	81,539
Investments in subsidiaries, on an equity-method basis	4,220	4,575
Operating lease assets	115,879	127,830
Goodwill	1,072,129	1,072,982	$ 924,837
Other assets	80,739	75,430
Total assets	2,702,861	2,737,879
Liabilities
Accounts payable and other liabilities	190,054	196,541
Operating lease liabilities	135,654	148,003
Notes payable	445,290	447,006
Total liabilities	1,324,312	1,367,614
Contingent liabilities and commitments
Stockholders’ equity
Common Stock – $1 par, authorized 51,500,000; issued 27,722,388 and 27,482,573; outstanding 27,370,227 and 27,130,412, respectively	27,723	27,483
Additional paid-in capital	310,728	296,861
Retained earnings	1,070,841	1,091,816
Accumulated other comprehensive income (loss) (AOCI):
Foreign currency translation adjustments	(18,579)	(23,856)
Net unrealized investment gains	(16,636)	(27,487)
Treasury stock – 352,161 common shares, at cost	(2,666)	(2,666)
Total stockholders’ equity	1,371,411	1,362,151
Total liabilities and stockholders' equity	2,702,861	2,737,879
Parent company
Assets
Cash and cash equivalents	6,070	31,912
Receivables from affiliates	50,183	49,055
Property and equipment, at cost:
Furniture and equipment	1,713	21
Accumulated depreciation	(190)	(21)
Total property and equipment, at cost	1,523	0
Investments in subsidiaries, on an equity-method basis	1,771,359	1,736,570
Operating lease assets	1,487	4,180
Goodwill	8,068	8,068
Other assets	17,495	16,730
Total assets	1,856,185	1,846,515
Liabilities
Accounts payable and other liabilities	27,255	24,036
Operating lease liabilities	2,389	5,720
Notes payable	455,130	454,608
Total liabilities	484,774	484,364
Contingent liabilities and commitments	0	0
Stockholders’ equity
Common Stock – $1 par, authorized 51,500,000; issued 27,722,388 and 27,482,573; outstanding 27,370,227 and 27,130,412, respectively	27,723	27,483
Additional paid-in capital	310,728	296,861
Retained earnings	1,070,841	1,091,816	$ 974,800	$ 688,819
Accumulated other comprehensive income (loss) (AOCI):
Foreign currency translation adjustments	(18,579)	(23,856)
Net unrealized investment gains	(16,636)	(27,487)
Treasury stock – 352,161 common shares, at cost	(2,666)	(2,666)
Total stockholders’ equity	1,371,411	1,362,151
Total liabilities and stockholders' equity	$ 1,856,185	$ 1,846,515