Segment Reporting (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Financial information for the Company's operating segments
Net interest income	$ 70,054	$ 48,781
Provision for loan losses	1,800	1,075
Noninterest income	33,302	21,870
Noninterest expense	69,814	47,319
Income before income taxes	31,742	22,257
Income taxes	10,526	7,017
Net income (loss)	21,216	15,240
Total assets	8,146,229	5,881,849	$ 7,926,496
Goodwill	449,425	274,705	445,871
Community Banks
Financial information for the Company's operating segments
Goodwill	446,658		443,104
Insurance
Financial information for the Company's operating segments
Goodwill	2,767		$ 2,767
Operating Segments | Community Banks
Financial information for the Company's operating segments
Net interest income	70,821	49,516
Provision for loan losses	1,813	1,078
Noninterest income	27,571	17,101
Noninterest expense	65,211	43,383
Income before income taxes	31,368	22,156
Income taxes	10,639	7,256
Net income (loss)	20,729	14,900
Total assets	8,053,379	5,800,703
Goodwill	446,658	271,938
Operating Segments | Insurance
Financial information for the Company's operating segments
Net interest income	86	69
Provision for loan losses	0	0
Noninterest income	3,000	2,395
Noninterest expense	1,736	1,621
Income before income taxes	1,350	843
Income taxes	530	320
Net income (loss)	820	523
Total assets	23,013	19,960
Goodwill	2,767	2,767
Operating Segments | Wealth Management
Financial information for the Company's operating segments
Net interest income	434	430
Provision for loan losses	(13)	(3)
Noninterest income	2,985	2,365
Noninterest expense	2,738	2,107
Income before income taxes	694	691
Income taxes	0	0
Net income (loss)	694	691
Total assets	46,645	43,958
Goodwill	0	0
Operating Segments | Other
Financial information for the Company's operating segments
Net interest income	(1,287)	(1,234)
Provision for loan losses	0	0
Noninterest income	(254)	9
Noninterest expense	129	208
Income before income taxes	(1,670)	(1,433)
Income taxes	(643)	(559)
Net income (loss)	(1,027)	(874)
Total assets	23,192	17,228
Goodwill	$ 0	$ 0