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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Changes in allowance for loan losses
Balance at beginning of period	$ 58,213	$ 52,300	$ 55,798	$ 48,075
Loans charged-off	(2,779)	(1,988)	(7,260)	(5,914)
Recoveries of loans previously charged off	884	582	2,833	2,687
Net charge-offs	(1,895)	(1,406)	(4,427)	(3,227)
Provision for loan losses charged to operations	4,028	3,117	9,220	10,049
Reduction due to loan removals	(91)	(174)	(336)	(1,060)
Balance at end of period	60,255	53,837	60,255	53,837
Non-acquired loans
Changes in allowance for loan losses
Balance at beginning of period	53,590	47,874	51,194	43,448
Loans charged-off	(1,969)	(1,891)	(4,541)	(4,300)
Recoveries of loans previously charged off	834	555	2,461	2,408
Net charge-offs	(1,135)	(1,336)	(2,080)	(1,892)
Provision for loan losses charged to operations	2,482	3,331	5,823	8,313
Balance at end of period	54,937	49,869	54,937	49,869
Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off	(810)	(97)	(2,719)	(1,614)
Recoveries of loans previously charged off	50	27	372	279
Net charge-offs	(760)	(70)	(2,347)	(1,335)
Provision for loan losses charged to operations	760	70	2,347	1,335
Acquired credit impaired loans
Changes in allowance for loan losses
Balance at beginning of period	4,623	4,426	4,604	4,627
Provision for loan losses charged to operations	786	(284)	1,050	401
Reduction due to loan removals	(91)	(174)	(336)	(1,060)
Balance at end of period	5,318	3,968	5,318	3,968
Residential real estate | Acquired credit impaired loans
Changes in allowance for loan losses
Reduction due to loan removals	(91)	(116)	(286)	(348)
Commercial owner occupied real estate loan | Non-acquired loans
Changes in allowance for loan losses
Loans charged-off	(31)	(578)	(43)	(659)
Recoveries of loans previously charged off	18	105	84	76
Provision for loan losses charged to operations	456	943	559	1,532
Commercial owner occupied real estate loan | Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off			(786)	(28)
Provision for loan losses charged to operations			786	28
Consumer loans | Acquired credit impaired loans
Changes in allowance for loan losses
Reduction due to loan removals				(3)
Commercial and industrial | Non-acquired loans
Changes in allowance for loan losses
Loans charged-off	(32)	(34)	(141)	(178)
Recoveries of loans previously charged off	77	27	286	241
Provision for loan losses charged to operations	21	219	(38)	1,372
Commercial and industrial | Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off	(648)	(30)	(1,288)	(838)
Recoveries of loans previously charged off	10	5	181	60
Provision for loan losses charged to operations	638	25	1,107	778
Commercial and industrial | Acquired credit impaired loans
Changes in allowance for loan losses
Reduction due to loan removals		(21)	(45)	(577)
Other income producing property | Non-acquired loans
Changes in allowance for loan losses
Loans charged-off			(31)
Recoveries of loans previously charged off	29	3	87	14
Provision for loan losses charged to operations	(29)	(6)	(143)	21
Other income producing property | Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off			(26)
Recoveries of loans previously charged off			71
Provision for loan losses charged to operations			(45)
Consumer | Non-acquired loans
Changes in allowance for loan losses
Loans charged-off	(1,727)	(1,163)	(4,035)	(3,237)
Recoveries of loans previously charged off	265	186	723	596
Provision for loan losses charged to operations	1,633	1,089	3,954	3,036
Consumer | Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off	(100)	(63)	(305)	(328)
Recoveries of loans previously charged off	9	14	36	63
Provision for loan losses charged to operations	91	49	269	265
Other loans | Non-acquired loans
Changes in allowance for loan losses
Provision for loan losses charged to operations		94	(41)	152
Construction and land development | Commercial non-owner occupied real estate | Non-acquired loans
Changes in allowance for loan losses
Loans charged-off	(69)		(78)	(35)
Recoveries of loans previously charged off	208	178	833	1,167
Provision for loan losses charged to operations	159	(352)	(421)	(1,040)
Construction and land development | Commercial non-owner occupied real estate | Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off	(39)		(45)	(106)
Recoveries of loans previously charged off	1	1	3	8
Provision for loan losses charged to operations	38	(1)	42	98
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)		(113)
Other commercial non-owner occupied real estate | Commercial non-owner occupied real estate | Non-acquired loans
Changes in allowance for loan losses
Loans charged-off			(3)
Recoveries of loans previously charged off	2	2	47	6
Provision for loan losses charged to operations	238	774	1,753	1,454
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)	(5)	(19)
Home equity loans | Consumer loans | Non-acquired loans
Changes in allowance for loan losses
Loans charged-off	(100)	(40)	(115)	(111)
Recoveries of loans previously charged off	86	11	220	139
Provision for loan losses charged to operations	28	102	(348)	163
Home equity loans | Consumer loans | Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off	(23)	(4)
Recoveries of loans previously charged off	9	6
Provision for loan losses charged to operations	14	(2)
Home equity loans | Commercial loans | Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off			(263)	(244)
Recoveries of loans previously charged off			55	85
Provision for loan losses charged to operations			208	159
Consumer Owner Occupied Loans | Consumer loans | Non-acquired loans
Changes in allowance for loan losses
Loans charged-off	(10)	(76)	(95)	(80)
Recoveries of loans previously charged off	149	43	181	169
Provision for loan losses charged to operations	(24)	468	548	1,623
Consumer Owner Occupied Loans | Consumer loans | Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off			(6)	(70)
Recoveries of loans previously charged off	21	1	26	63
Provision for loan losses charged to operations	$ (21)	$ (1)	$ (20)	$ 7