Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Financial information for the Company's operating segments
Net interest income	$ 48,842	$ 49,971
Provision for loan losses	1,075	1,450
Noninterest income	21,904	18,616
Noninterest expense	47,414	47,645
Income before income taxes	22,257	19,492
Income taxes	7,017	5,895
Net income	15,240	13,597
Total assets	5,881,849	5,902,831	5,805,129
Goodwill	274,705	276,144	274,706
Community Banks
Financial information for the Company's operating segments
Net interest income	49,593	50,636
Provision for loan losses	1,075	1,389
Noninterest income	17,136	14,083
Noninterest expense	43,691	44,125
Income before income taxes	21,963	19,205
Income taxes	7,256	5,978
Net income	14,707	13,227
Total assets	5,800,703	5,826,289
Goodwill	271,938	273,387
Insurance
Financial information for the Company's operating segments
Net interest income	69	63
Provision for loan losses	0	0
Noninterest income	2,395	2,393
Noninterest expense	1,621	1,474
Income before income taxes	843	982
Income taxes	320	380
Net income	523	602
Total assets	19,960	17,442
Goodwill	2,767	2,757
Wealth Management
Financial information for the Company's operating segments
Net interest income	415	311
Provision for loan losses	0	61
Noninterest income	2,364	2,116
Noninterest expense	1,894	1,868
Income before income taxes	885	498
Income taxes	0	0
Net income	885	498
Total assets	43,958	44,345
Goodwill	0	0
Other
Financial information for the Company's operating segments
Net interest income	(1,235)	(1,039)
Provision for loan losses	0	0
Noninterest income	9	24
Noninterest expense	208	178
Income before income taxes	(1,434)	(1,193)
Income taxes	(559)	(463)
Net income	(875)	(730)
Total assets	17,228	14,755
Goodwill	$ 0	$ 0