Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Financial information for the Company's operating segments
Net interest income	$ 34,404	$ 33,410	$ 67,785	$ 66,253
Provision for loan losses	3,000	4,700	6,050	9,500
Noninterest income	17,317	16,278	34,695	32,706
Noninterest expense	37,734	36,750	75,334	73,412
Income before income taxes	10,987	8,238	21,096	16,047
Income taxes	2,968	1,893	5,506	3,728
Net income	8,019	6,345	15,590	12,319
Total assets	4,249,281	4,112,377	4,249,281	4,112,377	4,178,616
Goodwill	184,779	184,879	184,779	184,879	184,859
Community Banks [Member]
Financial information for the Company's operating segments
Net interest income	34,251	33,661	67,928	66,766
Provision for loan losses	2,990	4,723	5,907	9,517
Noninterest income	15,102	13,793	30,122	27,079
Noninterest expense	34,921	34,179	70,023	68,483
Income before income taxes	11,442	8,552	22,120	15,845
Income taxes	3,079	2,055	5,802	3,787
Net income	8,363	6,497	16,318	12,058
Total assets	4,183,079	4,054,647	4,183,079	4,054,647
Goodwill	181,996	182,096	181,996	182,096
Insurance [Member]
Financial information for the Company's operating segments
Net interest income	24	24	47	48
Provision for loan losses	0	0	0	0
Noninterest income	973	901	2,006	2,070
Noninterest expense	813	793	1,626	1,576
Income before income taxes	184	132	427	542
Income taxes	71	51	165	210
Net income	113	81	262	332
Total assets	10,460	10,186	10,460	10,186
Goodwill	2,783	2,783	2,783	2,783
Wealth Management [Member]
Financial information for the Company's operating segments
Net interest income	324	341	619	704
Provision for loan losses	10	(23)	143	(17)
Noninterest income	1,237	1,563	2,541	3,514
Noninterest expense	1,736	1,646	3,317	3,112
Income before income taxes	(185)	281	(300)	1,123
Income taxes	0	63	0	289
Net income	(185)	218	(300)	834
Total assets	42,886	38,125	42,886	38,125
Goodwill	0	0	0	0
Other [Member]
Financial information for the Company's operating segments
Net interest income	(195)	(616)	(809)	(1,265)
Provision for loan losses	0	0	0	0
Noninterest income	5	21	26	43
Noninterest expense	264	132	368	241
Income before income taxes	(454)	(727)	(1,151)	(1,463)
Income taxes	(182)	(276)	(461)	(558)
Net income	(272)	(451)	(690)	(905)
Total assets	12,856	9,419	12,856	9,419
Goodwill	$ 0	$ 0	$ 0	$ 0