Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Financial information for the Company's operating segments
Net interest income	$ 50,472	$ 38,748	$ 152,612	$ 106,533
Provision for loan losses	2,217	2,300	5,117	8,350
Noninterest income	22,563	18,935	60,650	53,630
Noninterest expense	48,175	46,613	145,216	121,947
Income before income taxes	22,643	8,770	62,929	29,866
Income taxes	7,108	2,133	18,944	7,639
Net income	15,535	6,637	43,985	22,227
Total assets	5,751,711	5,736,048	5,751,711	5,736,048	5,746,270
Goodwill	274,658	275,328	274,658	275,328	276,100
Community Banks
Financial information for the Company's operating segments
Net interest income	51,298	39,133	154,678	107,061
Provision for loan losses	2,227	2,307	5,117	8,214
Noninterest income	17,551	16,160	46,763	46,282
Noninterest expense	44,130	43,590	133,785	113,613
Income before income taxes	22,492	9,396	62,539	31,516
Income taxes	7,251	2,428	19,397	8,230
Net income	15,241	6,968	43,142	23,286
Total assets	5,671,079	5,662,257	5,671,079	5,662,257
Goodwill	271,891	272,545	271,891	272,545
Insurance
Financial information for the Company's operating segments
Net interest income	65	29	177	76
Provision for loan losses	0	0	0	0
Noninterest income	2,261	1,428	6,792	3,434
Noninterest expense	1,656	1,021	4,814	2,647
Income before income taxes	670	436	2,155	863
Income taxes	262	77	844	242
Net income	408	359	1,311	621
Total assets	18,834	16,661	18,834	16,661
Goodwill	2,767	2,783	2,767	2,783
Wealth Management
Financial information for the Company's operating segments
Net interest income	338	331	969	950
Provision for loan losses	(10)	(7)	0	136
Noninterest income	2,353	1,325	6,650	3,866
Noninterest expense	2,176	1,768	6,043	5,085
Income before income taxes	525	(105)	1,576	(405)
Income taxes	0	0	0	0
Net income	525	(105)	1,576	(405)
Total assets	46,527	42,291	46,527	42,291
Goodwill	0	0	0	0
Other
Financial information for the Company's operating segments
Net interest income	(1,229)	(745)	(3,212)	(1,554)
Provision for loan losses	0	0	0	0
Noninterest income	398	22	445	48
Noninterest expense	213	234	574	602
Income before income taxes	(1,044)	(957)	(3,341)	(2,108)
Income taxes	(405)	(372)	(1,297)	(833)
Net income	(639)	(585)	(2,044)	(1,275)
Total assets	15,271	14,839	15,271	14,839
Goodwill	$ 0	$ 0	$ 0	$ 0