Parent Only Financial Information Parent Only Income Statement (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]      
Interest and Dividends on Investments $ 70,738 $ 66,861 $ 64,138
Other Operating Income 1,354 1,238 1,024
Net Gains on Securities Transactions 129 110 540
Interest Expense 4,813 5,767 7,922
Salaries and Employee Benefits 33,064 30,941 31,182
Other Operating Expense 13,913 12,980 12,656
Income Tax Benefit (10,610) (10,174) (9,079)
Net Income 24,662 23,360 21,795
Parent Company [Member]      
Condensed Financial Statements, Captions [Line Items]      
Dividends from Bank Subsidiaries 13,400 13,300 12,900
Interest and Dividends on Investments 118 116 116
Other Operating Income 847 578 549
Total Income 14,365 13,994 13,565
Interest Expense 619 620 640
Salaries and Employee Benefits 80 77 59
Other Operating Expense 885 754 860
Total Expense 1,584 1,451 1,559
Income Before Income Tax Benefit and Equity in Undistributed Net Income of Subsidiaries 12,781 12,543 12,006
Income Tax Benefit (372) (473) (634)
Equity in Undistributed Net Income of Subsidiaries 11,509 10,344 9,155
Net Income $ 24,662 $ 23,360 $ 21,795