Parent Company Statements of Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Interest and Dividend Income, Operating	$ 91,829	$ 94,589	$ 92,226	$ 81,856	$ 82,167	$ 80,229	$ 74,691	$ 73,714	$ 360,500	$ 310,801	$ 286,424
Gain (Loss) on Sale of Investments									(421)	(2,271)	1,821
Interest Expense	14,820	17,488	16,375	14,080	12,537	12,553	9,949	8,864	62,763	43,903	42,665
Income taxes									22,071	20,912	34,227
Net Income (Loss) Attributable to Parent	$ 23,936	$ 31,146	$ 22,163	$ 25,455	$ 26,261	$ 24,762	$ 28,241	$ 31,123	102,700	110,387	84,242
Other Comprehensive Income (Loss), Net of Tax									40,199	(18,533)	(8,709)
Parent Company
Dividends From Subsidiaries									97,500	100,000	60,000
Interest and Dividend Income, Operating									1,250	1,275	1,500
Gain (Loss) on Sale of Investments									0	0	1,821
Other Income									4,634	6,068	1,405
Revenues									103,384	107,343	64,726
Interest Expense									1,950	617	1,073
Other Expenses									19,804	14,619	8,805
Operating Expenses									21,754	15,236	9,878
Income Before Taxes And Equity In Undistributed Losses Of Subsidiaries									81,630	92,107	54,848
Income taxes									(4,242)	(4,010)	(2,695)
Income Before Equity In Undistributed Losses Of Subsidiaries									85,872	96,117	57,543
Equity In Undistributed Losses Of Subsidiaries									(16,828)	(14,270)	(26,699)
Net Income (Loss) Attributable to Parent									102,700	110,387	84,242
Other Comprehensive Income (Loss), Net of Tax									40,199	(18,533)	(8,709)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent									$ 142,899	$ 91,854	$ 75,533