Segment Reporting (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financial information for operating segments
Net interest income	$ 78,049	$ 75,731	$ 77,157	$ 70,054	$ 72,351	$ 68,612	$ 51,614	$ 48,781	$ 300,991	$ 241,358	$ 202,482
Provision for loan losses	1,650	2,650	1,430	1,800	1,750	750	1,175	1,075	7,530	4,750	6,167
Noninterest income	30,071	38,272	35,586	33,302	31,442	32,079	22,879	21,870	137,415	108,270	80,509
Noninterest expense	71,374	76,468	77,259	69,814	70,734	75,979	51,082	47,319	295,099	245,114	190,937
Income before income taxes	35,096	34,885	34,054	31,742	31,309	23,962	22,236	22,257	135,777	99,764	85,887
Income taxes	11,461	11,706	11,154	10,526	10,149	7,742	6,842	7,017	44,847	31,750	26,305
Net income	23,635	$ 23,179	$ 22,900	$ 21,216	21,160	$ 16,220	$ 15,394	$ 15,240	90,930	68,014	59,582
Total assets	8,699,851				7,926,496				8,699,851	7,926,496	5,805,129
Goodwill	470,534				445,871				470,534	445,871	274,706
Community Banks
Financial information for operating segments
Goodwill	467,767				443,104				467,767	443,104	271,939
Insurance
Financial information for operating segments
Goodwill	2,767				2,767				2,767	2,767	2,767
Operating Segments | Community Banks
Financial information for operating segments
Net interest income									305,583	244,242	205,353
Provision for loan losses									7,530	4,752	6,249
Noninterest income									114,615	88,498	61,973
Noninterest expense									276,260	228,248	175,660
Income before income taxes									136,408	99,740	85,417
Income taxes									46,352	32,941	27,037
Net income									90,056	66,799	58,380
Total assets	8,602,022				7,833,084				8,602,022	7,833,084	5,720,995
Goodwill	467,767				443,104				467,767	443,104	271,939
Operating Segments | Insurance
Financial information for operating segments
Net interest income									350	311	237
Provision for loan losses									0	0	0
Noninterest income									10,074	9,340	9,055
Noninterest expense									6,873	6,900	6,441
Income before income taxes									3,551	2,751	2,851
Income taxes									1,385	1,078	1,114
Net income									2,166	1,673	1,737
Total assets	23,693				22,550				23,693	22,550	20,472
Goodwill	2,767				2,767				2,767	2,767	2,767
Operating Segments | Wealth Management
Financial information for operating segments
Net interest income									1,846	1,688	1,332
Provision for loan losses									0	(2)	(82)
Noninterest income									12,354	10,559	8,997
Noninterest expense									11,099	9,130	8,111
Income before income taxes									3,101	3,119	2,300
Income taxes									0	0	0
Net income									3,101	3,119	2,300
Total assets	54,857				46,035				54,857	46,035	44,275
Goodwill	0				0				0	0	0
Other
Financial information for operating segments
Net interest income									(6,788)	(4,883)	(4,440)
Provision for loan losses									0	0	0
Noninterest income									372	(127)	484
Noninterest expense									867	836	725
Income before income taxes									(7,283)	(5,846)	(4,681)
Income taxes									(2,890)	(2,269)	(1,846)
Net income									(4,393)	(3,577)	(2,835)
Total assets	19,279				24,827				19,279	24,827	19,387
Goodwill	$ 0				$ 0				$ 0	$ 0	$ 0