Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Financial information for the Company's operating segments
Net interest income	$ 38,748	$ 33,132	$ 106,533	$ 99,385
Provision for loan losses	2,300	4,625	8,350	14,125
Noninterest income	18,935	18,055	53,630	50,761
Noninterest expense	46,613	38,672	121,947	112,084
Income before income taxes	8,770	7,890	29,866	23,937
Income taxes	2,133	853	7,639	4,581
Net income	6,637	7,037	22,227	19,356
Total assets	5,736,048	4,164,606	5,736,048	4,164,606	4,178,616
Goodwill	275,328	184,859	275,328	184,859	184,859
Community Banks [Member]
Financial information for the Company's operating segments
Net interest income	39,133	33,444	107,061	100,210
Provision for loan losses	2,307	4,659	8,214	14,176
Noninterest income	16,160	15,428	46,282	42,507
Noninterest expense	43,590	36,042	113,613	104,525
Income before income taxes	9,396	8,171	31,516	24,016
Income taxes	2,428	1,203	8,230	4,990
Net income	6,968	6,968	23,286	19,026
Total assets	5,662,257	4,105,716	5,662,257	4,105,716
Goodwill	272,545	182,076	272,545	182,076
Insurance [Member]
Financial information for the Company's operating segments
Net interest income	29	23	76	71
Provision for loan losses	0	0	0	0
Noninterest income	1,428	887	3,434	2,957
Noninterest expense	1,021	786	2,647	2,362
Income before income taxes	436	124	863	666
Income taxes	77	48	242	258
Net income	359	76	621	408
Total assets	16,661	10,725	16,661	10,725
Goodwill	2,783	2,783	2,783	2,783
Wealth Management [Member]
Financial information for the Company's operating segments
Net interest income	331	314	950	1,018
Provision for loan losses	(7)	(34)	136	(51)
Noninterest income	1,325	1,720	3,866	5,234
Noninterest expense	1,768	1,661	5,085	4,773
Income before income taxes	(105)	407	(405)	1,530
Income taxes	0	51	0	340
Net income	(105)	356	(405)	1,190
Total assets	42,291	35,172	42,291	35,172
Goodwill	0	0	0	0
Other [Member]
Financial information for the Company's operating segments
Net interest income	(745)	(649)	(1,554)	(1,914)
Provision for loan losses	0	0	0	0
Noninterest income	22	20	48	63
Noninterest expense	234	183	602	424
Income before income taxes	(957)	(812)	(2,108)	(2,275)
Income taxes	(372)	(449)	(833)	(1,007)
Net income	(585)	(363)	(1,275)	(1,268)
Total assets	14,839	12,993	14,839	12,993
Goodwill	$ 0	$ 0	$ 0	$ 0