Loans and Allowance for Loan Losses - Aggregated analysis of the changes in allowance for loan losses - (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Changes in allowance for loan losses
Balance at beginning of period	$ 52,300	$ 43,890	$ 48,075	$ 40,355
Loans charged-off	(1,988)	(1,658)	(5,914)	(5,137)
Recoveries of loans previously charged off	582	1,115	2,687	2,455
Net charge-offs	(1,406)	(543)	(3,227)	(2,682)
Provision for loan losses charged to operations	3,117	2,062	10,049	8,082
Reduction due to loan removals	(174)	(198)	(1,060)	(544)
Balance at end of period	53,837	45,211	53,837	45,211
Non-acquired loans
Changes in allowance for loan losses
Balance at beginning of period	47,874	40,149	43,448	36,960
Loans charged-off	(1,891)	(1,383)	(4,300)	(3,972)
Recoveries of loans previously charged off	555	836	2,408	2,041
Net charge-offs	(1,336)	(547)	(1,892)	(1,931)
Provision for loan losses charged to operations	3,331	1,939	8,313	6,512
Balance at end of period	49,869	41,541	49,869	41,541
Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off	(97)	(275)	(1,614)	(1,165)
Recoveries of loans previously charged off	27	279	279	414
Net charge-offs	(70)	4	(1,335)	(751)
Provision for loan losses charged to operations	70	(4)	1,335	751
Acquired credit impaired loans
Changes in allowance for loan losses
Balance at beginning of period	4,426	3,741	4,627	3,395
Provision for loan losses charged to operations	(284)	127	401	819
Reduction due to loan removals	(174)	(198)	(1,060)	(544)
Balance at end of period	3,968	3,670	3,968	3,670
Residential real estate | Acquired credit impaired loans
Changes in allowance for loan losses
Reduction due to loan removals	(116)	(149)	(348)	(386)
Commercial owner occupied real estate loan | Non-acquired loans
Changes in allowance for loan losses
Loans charged-off	(578)		(659)
Recoveries of loans previously charged off	105	92	76	197
Provision for loan losses charged to operations	943	479	1,532	(109)
Commercial owner occupied real estate loan | Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off			(28)
Recoveries of loans previously charged off		1		1
Provision for loan losses charged to operations		(1)	28	(1)
Consumer loans | Acquired credit impaired loans
Changes in allowance for loan losses
Reduction due to loan removals		(1)	(3)	(11)
Commercial and industrial | Non-acquired loans
Changes in allowance for loan losses
Loans charged-off	(34)	(440)	(178)	(629)
Recoveries of loans previously charged off	27	31	241	264
Provision for loan losses charged to operations	219	469	1,372	726
Commercial and industrial | Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off	(30)	(1)	(838)	(3)
Recoveries of loans previously charged off	5	1	60	3
Provision for loan losses charged to operations	25		778
Commercial and industrial | Acquired credit impaired loans
Changes in allowance for loan losses
Reduction due to loan removals	(21)	(12)	(577)	(66)
Other income producing property | Non-acquired loans
Changes in allowance for loan losses
Loans charged-off		(10)		(17)
Recoveries of loans previously charged off	3	29	14	77
Provision for loan losses charged to operations	(6)	(10)	21	(214)
Other income producing property | Acquired non-credit impaired loans
Changes in allowance for loan losses
Recoveries of loans previously charged off				1
Provision for loan losses charged to operations				(1)
Consumer | Non-acquired loans
Changes in allowance for loan losses
Loans charged-off	(1,163)	(897)	(3,237)	(2,407)
Recoveries of loans previously charged off	186	168	596	546
Provision for loan losses charged to operations	1,089	889	3,036	2,203
Consumer | Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off	(63)	(123)	(328)	(337)
Recoveries of loans previously charged off	14	2	63	21
Provision for loan losses charged to operations	49	121	265	316
Other loans | Non-acquired loans
Changes in allowance for loan losses
Provision for loan losses charged to operations	94	(114)	152	(386)
Construction and land development | Commercial non-owner occupied real estate | Non-acquired loans
Changes in allowance for loan losses
Loans charged-off		(19)	(35)	(493)
Recoveries of loans previously charged off	178	333	1,167	555
Provision for loan losses charged to operations	(352)	(88)	(1,040)	1,819
Construction and land development | Commercial non-owner occupied real estate | Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off			(106)
Recoveries of loans previously charged off	1	1	8	3
Provision for loan losses charged to operations	(1)	(1)	98	(3)
Construction and land development | Commercial non-owner occupied real estate | Acquired credit impaired loans
Changes in allowance for loan losses
Reduction due to loan removals	(31)	(36)	(113)	(80)
Other commercial non-owner occupied real estate | Commercial non-owner occupied real estate | Non-acquired loans
Changes in allowance for loan losses
Recoveries of loans previously charged off	2	80	6	128
Provision for loan losses charged to operations	774	(7)	1,454	1,129
Other commercial non-owner occupied real estate | Commercial non-owner occupied real estate | Acquired credit impaired loans
Changes in allowance for loan losses
Reduction due to loan removals	(6)		(19)	(1)
Home equity loans | Commercial owner occupied real estate loan | Non-acquired loans
Changes in allowance for loan losses
Loans charged-off			(111)	(241)
Recoveries of loans previously charged off			139	133
Provision for loan losses charged to operations			163	(6)
Home equity loans | Consumer loans | Non-acquired loans
Changes in allowance for loan losses
Loans charged-off	(40)	(17)
Recoveries of loans previously charged off	11	38
Provision for loan losses charged to operations	102	(171)
Home equity loans | Consumer loans | Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off	(4)	(71)	(244)	(736)
Recoveries of loans previously charged off	6	274	85	343
Provision for loan losses charged to operations	(2)	(203)	159	393
Consumer Owner Occupied Loans | Consumer loans | Non-acquired loans
Changes in allowance for loan losses
Loans charged-off	(76)		(80)	(185)
Recoveries of loans previously charged off	43	65	169	141
Provision for loan losses charged to operations	468	492	1,623	1,350
Consumer Owner Occupied Loans | Consumer loans | Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off		(80)	(70)	(89)
Recoveries of loans previously charged off	1		63	42
Provision for loan losses charged to operations	$ (1)	$ 80	$ 7	$ 47