Loans and Allowance for Loan Losses - Credit risk profile by risk grade of non acquired loans - (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Loans and Allowance for Loan Losses
Other Real Estate, Non Covered	$ 22,427	$ 4,200	$ 24,803	$ 26,870	$ 26,499
Non-acquired loans
Loans and Allowance for Loan Losses
Total loans	4,816,875		4,220,726	3,788,399
Non-acquired loans | Pass
Loans and Allowance for Loan Losses
Total loans	4,665,729		4,077,013	3,624,075
Non-acquired loans | Special mention
Loans and Allowance for Loan Losses
Total loans	108,107		96,261	109,455
Non-acquired loans | Substandard
Loans and Allowance for Loan Losses
Total loans	43,039		47,430	54,847
Non-acquired loans | Doubtful
Loans and Allowance for Loan Losses
Total loans			22	22
Non-acquired loans | Commercial non-owner occupied real estate
Loans and Allowance for Loan Losses
Total loans	1,120,047		889,756	720,478
Non-acquired loans | Commercial non-owner occupied real estate | Construction and land development
Loans and Allowance for Loan Losses
Total loans	533,219		401,979	368,954
Non-acquired loans | Commercial non-owner occupied real estate | Construction and land development | Pass
Loans and Allowance for Loan Losses
Total loans	518,537		382,167	344,314
Non-acquired loans | Commercial non-owner occupied real estate | Construction and land development | Special mention
Loans and Allowance for Loan Losses
Total loans	9,230		13,633	16,561
Non-acquired loans | Commercial non-owner occupied real estate | Construction and land development | Substandard
Loans and Allowance for Loan Losses
Total loans	5,452		6,179	8,079
Non-acquired loans | Commercial non-owner occupied real estate | Other commercial non-owner occupied real estate
Loans and Allowance for Loan Losses
Total loans	586,828		487,777	351,524
Non-acquired loans | Commercial non-owner occupied real estate | Other commercial non-owner occupied real estate | Pass
Loans and Allowance for Loan Losses
Total loans	569,815		471,466	331,279
Non-acquired loans | Commercial non-owner occupied real estate | Other commercial non-owner occupied real estate | Special mention
Loans and Allowance for Loan Losses
Total loans	14,859		13,912	16,885
Non-acquired loans | Commercial non-owner occupied real estate | Other commercial non-owner occupied real estate | Substandard
Loans and Allowance for Loan Losses
Total loans	2,154		2,399	3,360
Non-acquired loans | Commercial owner occupied real estate loan
Loans and Allowance for Loan Losses
Total loans	1,083,051		1,033,398	975,701
Non-acquired loans | Commercial owner occupied real estate loan | Pass
Loans and Allowance for Loan Losses
Total loans	1,041,512		994,442	927,678
Non-acquired loans | Commercial owner occupied real estate loan | Special mention
Loans and Allowance for Loan Losses
Total loans	31,631		29,478	34,974
Non-acquired loans | Commercial owner occupied real estate loan | Substandard
Loans and Allowance for Loan Losses
Total loans	9,908		9,478	13,049
Non-acquired loans | Consumer real estate
Loans and Allowance for Loan Losses
Total loans	1,455,624		1,338,239	1,207,047
Non-acquired loans | Consumer real estate | Home equity loans
Loans and Allowance for Loan Losses
Total loans	345,957		319,255	300,074
Non-acquired loans | Consumer real estate | Home equity loans | Pass
Loans and Allowance for Loan Losses
Total loans	330,270		304,744	286,603
Non-acquired loans | Consumer real estate | Home equity loans | Special mention
Loans and Allowance for Loan Losses
Total loans	8,341		8,171	7,634
Non-acquired loans | Consumer real estate | Home equity loans | Substandard
Loans and Allowance for Loan Losses
Total loans	7,346		6,318	5,815
Non-acquired loans | Consumer real estate | Home equity loans | Doubtful
Loans and Allowance for Loan Losses
Total loans			22	22
Non-acquired loans | Consumer real estate | Consumer
Loans and Allowance for Loan Losses
Total loans	1,820,173		1,617,916	1,480,532
Non-acquired loans | Consumer real estate | Consumer | Pass
Loans and Allowance for Loan Losses
Total loans	1,771,864		1,567,391	1,428,513
Non-acquired loans | Consumer real estate | Consumer | Special mention
Loans and Allowance for Loan Losses
Total loans	26,907		26,719	27,207
Non-acquired loans | Consumer real estate | Consumer | Substandard
Loans and Allowance for Loan Losses
Total loans	21,402		23,784	24,790
Non-acquired loans | Consumer real estate | Consumer | Doubtful
Loans and Allowance for Loan Losses
Total loans			22	22
Non-acquired loans | Consumer real estate | Consumer Owner Occupied Loans
Loans and Allowance for Loan Losses
Total loans	1,109,667		1,018,984	906,973
Non-acquired loans | Consumer real estate | Consumer Owner Occupied Loans | Pass
Loans and Allowance for Loan Losses
Total loans	1,078,749		984,780	870,005
Non-acquired loans | Consumer real estate | Consumer Owner Occupied Loans | Special mention
Loans and Allowance for Loan Losses
Total loans	17,814		17,777	18,679
Non-acquired loans | Consumer real estate | Consumer Owner Occupied Loans | Substandard
Loans and Allowance for Loan Losses
Total loans	13,104		16,427	18,289
Non-acquired loans | Commercial and industrial
Loans and Allowance for Loan Losses
Total loans	611,901		503,808	448,247
Non-acquired loans | Commercial and industrial | Pass
Loans and Allowance for Loan Losses
Total loans	596,879		497,572	442,354
Non-acquired loans | Commercial and industrial | Special mention
Loans and Allowance for Loan Losses
Total loans	13,441		4,472	4,497
Non-acquired loans | Commercial and industrial | Substandard
Loans and Allowance for Loan Losses
Total loans	1,581		1,764	1,396
Non-acquired loans | Other income producing property
Loans and Allowance for Loan Losses
Total loans	181,703		175,848	163,441
Non-acquired loans | Other income producing property | Pass
Loans and Allowance for Loan Losses
Total loans	167,122		163,975	149,937
Non-acquired loans | Other income producing property | Special mention
Loans and Allowance for Loan Losses
Total loans	12,039		8,047	9,331
Non-acquired loans | Other income producing property | Substandard
Loans and Allowance for Loan Losses
Total loans	2,542		3,826	4,173
Non-acquired loans | Consumer
Loans and Allowance for Loan Losses
Total loans	272,957		233,104	209,544
Non-acquired loans | Consumer | Pass
Loans and Allowance for Loan Losses
Total loans	271,253		231,294	207,964
Non-acquired loans | Consumer | Special mention
Loans and Allowance for Loan Losses
Total loans	752		771	894
Non-acquired loans | Consumer | Substandard
Loans and Allowance for Loan Losses
Total loans	952		1,039	686
Non-acquired loans | Commercial
Loans and Allowance for Loan Losses
Total loans	2,996,702		2,602,810	2,307,867
Non-acquired loans | Commercial | Pass
Loans and Allowance for Loan Losses
Total loans	2,893,865		2,509,622	2,195,562
Non-acquired loans | Commercial | Special mention
Loans and Allowance for Loan Losses
Total loans	81,200		69,542	82,248
Non-acquired loans | Commercial | Substandard
Loans and Allowance for Loan Losses
Total loans	21,637		23,646	30,057
Non-acquired loans | Other loans
Loans and Allowance for Loan Losses
Total loans	91,592		46,573	63,941
Non-acquired loans | Other loans | Pass
Loans and Allowance for Loan Losses
Total loans	91,592		$ 46,573	63,941
Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total loans	662,587			828,670
Acquired credit impaired loans | Residential real estate
Loans and Allowance for Loan Losses
Total loans	285,518			348,687
Acquired credit impaired loans | Commercial non-owner occupied real estate | Construction and land development
Loans and Allowance for Loan Losses
Total loans	48,274			59,819
Acquired credit impaired loans | Commercial non-owner occupied real estate | Other commercial non-owner occupied real estate
Loans and Allowance for Loan Losses
Total loans	225,460			288,756
Acquired credit impaired loans | Consumer real estate
Loans and Allowance for Loan Losses
Total loans	64,114			77,083
Acquired credit impaired loans | Commercial and industrial
Loans and Allowance for Loan Losses
Total loans	27,961			38,894
Acquired credit impaired loans | Single pay loans
Loans and Allowance for Loan Losses
Total loans				58
Acquired credit impaired loans | Commercial loans 1000000 or more
Loans and Allowance for Loan Losses
Total loans	11,260			15,373
Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total loans	941,886			1,171,672
Acquired non-credit impaired loans | Commercial non-owner occupied real estate | Construction and land development
Loans and Allowance for Loan Losses
Total loans	12,516			17,762
Acquired non-credit impaired loans | Commercial non-owner occupied real estate | Other commercial non-owner occupied real estate
Loans and Allowance for Loan Losses
Total loans	36,904			43,123
Acquired non-credit impaired loans | Commercial owner occupied real estate loan
Loans and Allowance for Loan Losses
Total loans	32,267			49,334
Acquired non-credit impaired loans | Consumer real estate | Home equity loans
Loans and Allowance for Loan Losses
Total loans	177,946			210,734
Acquired non-credit impaired loans | Consumer real estate | Consumer Owner Occupied Loans
Loans and Allowance for Loan Losses
Total loans	466,479			574,697
Acquired non-credit impaired loans | Commercial and industrial
Loans and Allowance for Loan Losses
Total loans	15,598			31,762
Acquired non-credit impaired loans | Other income producing property
Loans and Allowance for Loan Losses
Total loans	44,873			58,987
Acquired non-credit impaired loans | Consumer
Loans and Allowance for Loan Losses
Total loans	$ 155,303			$ 185,273