Schedule I - Financial Information of the Registrant (Parent Company) - Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Assets
Cash and cash equivalents	$ 432,683	$ 330,609
Receivables:
Notes - due from subsidiaries	1,557	2,464
Total receivables	87,812	72,003
Property and equipment, at cost:
Furniture and equipment	168,147	178,416
Accumulated depreciation	(142,038)	(151,483)
Total property and equipment, at cost	51,671	50,461
Investments in subsidiaries, on an equity-method basis	6,765	6,169
Operating lease assets	106,479	99,028
Goodwill	431,477	248,890
Other assets	42,048	35,402
Total assets	1,978,575	1,592,785
Liabilities
Accounts payable and other liabilities	225,180	126,779
Operating lease liabilities	119,089	113,843
Notes payable	101,773	110,632
Total liabilities	966,169	839,026
Contingent liabilities and commitments
Stockholders’ equity
Common Stock – $1 par, authorized 51,500,000; issued 27,080,403 and 24,061,568; outstanding 26,728,242 and 23,709,407, respectively	27,080	24,062
Additional paid-in capital	274,857	164,217
Retained earnings	688,819	564,392
Accumulated other comprehensive income (loss) (AOCI):
Foreign currency translation adjustments	(8,238)	(13,027)
Net unrealized investment gains	25,260	10,328
Treasury stock – 352,161 common shares, at cost	(2,666)	(2,666)
Total stockholders’ equity	1,005,112	747,306
Total liabilities and stockholders' equity	1,978,575	1,592,785
Parent company
Assets
Cash and cash equivalents	3,604	36,849
Receivables:
Notes - due from subsidiaries	45,193	5,193
Receivables from affiliates	2,258	260
Total receivables	47,451	5,453
Property and equipment, at cost:
Furniture and equipment	75	88
Accumulated depreciation	(74)	(83)
Total property and equipment, at cost	1	5
Investments in subsidiaries, on an equity-method basis	1,055,154	802,994
Operating lease assets	7,439	8,931
Goodwill	8,068	8,470
Other assets	16,339	15,810
Total assets	1,138,056	878,512
Liabilities
Accounts payable and other liabilities	24,040	21,417
Operating lease liabilities	10,029	10,914
Notes payable	98,875	98,875
Total liabilities	132,944	131,206
Contingent liabilities and commitments	0	0
Stockholders’ equity
Common Stock – $1 par, authorized 51,500,000; issued 27,080,403 and 24,061,568; outstanding 26,728,242 and 23,709,407, respectively	27,080	24,062
Additional paid-in capital	274,857	164,217
Retained earnings	688,819	564,392	$ 514,248	$ 491,698
Accumulated other comprehensive income (loss) (AOCI):
Foreign currency translation adjustments	(8,238)	(13,027)
Net unrealized investment gains	25,260	10,328
Treasury stock – 352,161 common shares, at cost	(2,666)	(2,666)
Total stockholders’ equity	1,005,112	747,306
Total liabilities and stockholders' equity	$ 1,138,056	$ 878,512