Condensed Financial Information of Parent Company, Condensed Balance Sheets (Details) - USD ($)	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Assets [Abstract]
Short-term investments	$ 57,321,111	$ 12,692,341
Cash	25,123,332	57,709,375
Property and equipment	2,755,105	2,956,930
Other	1,123,098	1,612,732
Total assets	2,243,349,335	2,255,175,399
Liabilities [Abstract]
Cash dividends declared to stockholders	5,296,990	4,915,268
Other	7,864,942	7,557,757
Total liabilities	1,759,756,323	1,724,139,312
Stockholders' equity	483,593,012	531,036,087	$ 517,774,120	$ 451,015,519
Total liabilities and stockholders' equity	2,243,349,335	2,255,175,399
Parent Company [Member]
Assets [Abstract]
Investment in subsidiaries/affiliates (equity method)	509,513,000	554,804,000
Short-term investments	7,325,000	9,000
Cash	3,288,000	14,375,000	$ 15,321,000	$ 2,350,000
Property and equipment	586,000	716,000
Other	4,589,000	2,455,000
Total assets	525,301,000	572,359,000
Liabilities [Abstract]
Cash dividends declared to stockholders	5,297,000	4,915,000
Notes payable to subsidiary	35,000,000	35,000,000
Other	1,411,000	1,408,000
Total liabilities	41,708,000	41,323,000
Stockholders' equity	483,593,000	531,036,000
Total liabilities and stockholders' equity	$ 525,301,000	$ 572,359,000