Loans and Allowance for Loan Losses - Summary of acquired non credit impaired loans - (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014
Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	$ 662,587		$ 737,576	$ 828,670
Less allowance for loan losses	(3,752)	$ (3,877)	(3,706)	(4,689)	$ (4,717)
Acquired loans, net	658,835		733,870	823,981		$ 919,402
Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	941,886		1,049,538	1,171,672
Unamortized Discounts	14,000		16,800	20,200
Residential real estate | Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	285,518		313,319	348,687
Less allowance for loan losses	(2,592)	(2,863)		(3,184)	(3,320)
Commercial non-owner occupied real estate | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	49,420		53,952	60,885
Commercial owner occupied real estate loan | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	32,267		39,220	49,334
Consumer real estate | Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	64,114		70,734	77,083
Less allowance for loan losses	(778)	(606)		(449)	(244)
Consumer real estate | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	644,425		709,075	785,431
Commercial and industrial | Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	27,961		31,193	38,894
Less allowance for loan losses	(196)	(208)		(197)	(219)
Commercial and industrial | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	15,598		25,475	31,762
Other income producing property | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	44,873		51,169	58,987
Consumer | Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	64,114		70,734	77,083
Consumer | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	155,303		170,647	185,273
Commercial | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	142,158		169,816	200,968
Single pay loans | Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans				58
Less allowance for loan losses				(49)	(49)
Commercial loans 1000000 or more | Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	11,260		12,628	15,373
Less allowance for loan losses				66	64
Construction and land development | Commercial non-owner occupied real estate | Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	48,274		54,272	59,819
Less allowance for loan losses	(151)	(154)		(344)	(400)
Construction and land development | Commercial non-owner occupied real estate | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	12,516		13,849	17,762
Other commercial non-owner occupied real estate | Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans			255,430
Other commercial non-owner occupied real estate | Commercial non-owner occupied real estate | Acquired credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	225,460		255,430	288,756
Less allowance for loan losses	(35)	$ (46)		(532)	$ (549)
Other commercial non-owner occupied real estate | Commercial non-owner occupied real estate | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	36,904		40,103	43,123
Home equity loans | Consumer real estate | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	177,946		190,968	210,734
Consumer | Consumer real estate | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	155,303		170,647	185,273
Other Consumer | Consumer real estate | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	799,728		879,722	970,704
Consumer Owner Occupied Loans | Consumer real estate | Acquired non-credit impaired loans
Loans and Allowance for Loan Losses
Total acquired loans	$ 466,479		$ 518,107	$ 574,697