Parent Only Financial Information Parent Only Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
ASSETS
Interest-Bearing Deposits at Banks	$ 30,276	$ 14,331
Available-for-Sale	300,200	346,996
Held-to-Maturity (Approximate Fair Value of $335,901 at December 31, 2017, and $343,751 at December 31, 2016)	335,907	345,427
Other Assets	57,606	56,789
Total Assets	2,760,465	2,605,242
LIABILITIES
Junior Subordinated Obligations Issued to Unconsolidated Subsidiary Trusts	20,000	20,000
Other Liabilities	20,780	22,008
Total Liabilities	2,510,862	2,372,390
Equity [Abstract]
Stockholders' Equity Attributable to Parent	249,603	232,852	$ 213,971	$ 200,926
Total Liabilities and Stockholders' Equity	2,760,465	2,605,242
Parent Company [Member]
ASSETS
Interest-Bearing Deposits at Banks	2,186	3,593
Available-for-Sale	1,562	1,382
Held-to-Maturity (Approximate Fair Value of $335,901 at December 31, 2017, and $343,751 at December 31, 2016)	0	1,000
Equity Method Investments	261,622	243,031
Other Assets	7,987	7,951
Total Assets	273,357	256,957
LIABILITIES
Junior Subordinated Obligations Issued to Unconsolidated Subsidiary Trusts	20,000	20,000
Other Liabilities	3,754	4,105
Total Liabilities	23,754	24,105
Equity [Abstract]
Stockholders' Equity Attributable to Parent	249,603	232,852
Total Liabilities and Stockholders' Equity	$ 273,357	$ 256,957