Parent Only Financial Information Parent Only Income Statement (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Interest and Dividends on Investments	$ 76,915	$ 70,738	$ 66,861
Other Operating Income	1,113	1,354	1,238
Interest Expense	5,356	4,813	5,767
Salaries and Employee Benefits	34,330	33,064	30,941
Other Operating Expense	14,801	13,913	12,980
Income Tax Benefit	(11,215)	(10,610)	(10,174)
Net Income	26,534	24,662	23,360
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Dividends from Bank Subsidiaries	11,650	13,400	13,300
Interest and Dividends on Investments	117	118	116
Other Operating Income	635	847	578
Total Income	12,402	14,365	13,994
Interest Expense	691	619	620
Salaries and Employee Benefits	77	80	77
Other Operating Expense	865	885	754
Total Expense	1,633	1,584	1,451
Income Before Income Tax Benefit and Equity in Undistributed Net Income of Subsidiaries	10,769	12,781	12,543
Income Tax Benefit	(482)	(372)	(473)
Equity in Undistributed Net Income of Subsidiaries	15,283	11,509	10,344
Net Income	$ 26,534	$ 24,662	$ 23,360