Segments (Details) (USD $)	3 Months Ended												12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Selected financial information by business segment
Goodwill related to the 1996 purchase of a bank in southern Indiana	$ 682,000				$ 682,000								$ 682,000	$ 682,000
Net interest income	19,843,000	20,017,000	18,975,000	18,463,000	18,310,000	18,795,000	18,295,000	18,550,000	18,016,000	17,790,000	17,611,000	17,315,000	77,298,000	73,950,000	70,732,000
Provision for loan losses	1,575,000	1,325,000	1,325,000	2,325,000	2,475,000	2,475,000	2,475,000	4,075,000	3,100,000	4,100,000	2,600,000	2,800,000	6,550,000	11,500,000	12,600,000
Investment management and trust services													16,287,000	14,278,000	13,841,000
All other non-interest income													22,715,000	24,179,000	19,403,000
Non-interest expense	19,380,000	17,571,000	18,822,000	15,579,000	17,183,000	17,045,000	16,508,000	14,736,000	16,727,000	13,302,000	14,725,000	14,827,000	71,352,000	65,472,000	59,581,000
Income before income taxes	8,699,000	10,773,000	9,139,000	9,787,000	8,779,000	9,070,000	8,602,000	8,984,000	7,418,000	8,246,000	8,438,000	7,693,000	38,398,000	35,435,000	31,795,000
Tax expense	2,386,000	3,091,000	2,732,000	3,019,000	2,265,000	2,388,000	2,499,000	2,482,000	1,076,000	2,472,000	2,441,000	2,202,000	11,228,000	9,634,000	8,191,000
Net income	6,313,000	7,682,000	6,407,000	6,768,000	6,514,000	6,682,000	6,103,000	6,502,000	6,342,000	5,774,000	5,997,000	5,491,000	27,170,000	25,801,000	23,604,000
Operating Segments | Commercial banking
Selected financial information by business segment
Goodwill related to the 1996 purchase of a bank in southern Indiana	682,000												682,000
Net interest income													77,144,000	73,800,000	70,592,000
Provision for loan losses													6,550,000	11,500,000	12,600,000
All other non-interest income													22,654,000	24,110,000	19,382,000
Non-interest expense													61,891,000	57,323,000	51,863,000
Income before income taxes													31,357,000	29,087,000	25,511,000
Tax expense													8,740,000	7,412,000	5,992,000
Net income													22,617,000	21,675,000	19,519,000
Operating Segments | Investment management and trust
Selected financial information by business segment
Net interest income													154,000	150,000	140,000
Investment management and trust services													16,287,000	14,278,000	13,841,000
All other non-interest income													61,000	69,000	21,000
Non-interest expense													9,461,000	8,149,000	7,718,000
Income before income taxes													7,041,000	6,348,000	6,284,000
Tax expense													2,488,000	2,222,000	2,199,000
Net income													$ 4,553,000	$ 4,126,000	$ 4,085,000