Loans and Allowance for Loan Losses - Aggregated analysis of the changes in allowance for loan losses - (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Changes in allowance for loan losses
Balance at beginning of period	$ 49,287	$ 43,005	$ 48,075	$ 40,355
Loans charged-off	(2,423)	(1,793)	(3,926)	(3,479)
Recoveries of loans previously charged off	1,138	608	2,105	1,340
Net charge-offs	(1,285)	(1,185)	(1,821)	(2,139)
Provision for loan losses charged to operations	4,478	2,313	6,932	6,020
Reduction due to loan removals	(180)	(243)	(886)	(346)
Balance at end of period	52,300	43,890	52,300	43,890
Non-acquired loans
Changes in allowance for loan losses
Balance at beginning of period	45,203	38,449	43,448	36,960
Loans charged-off	(1,240)	(1,292)	(2,409)	(2,589)
Recoveries of loans previously charged off	1,051	536	1,853	1,205
Net charge-offs	(189)	(756)	(556)	(1,384)
Provision for loan losses charged to operations	2,860	2,456	4,982	4,573
Balance at end of period	47,874	40,149	47,874	40,149
Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off	(1,183)	(501)	(1,517)	(890)
Recoveries of loans previously charged off	87	72	252	135
Net charge-offs	(1,096)	(429)	(1,265)	(755)
Provision for loan losses charged to operations	1,096	429	1,265	755
Acquired credit impaired loans
Changes in allowance for loan losses
Balance at beginning of period	4,084	4,556	4,627	3,395
Provision for loan losses charged to operations	522	(572)	685	692
Reduction due to loan removals	(180)	(243)	(886)	(346)
Balance at end of period	4,426	3,741	4,426	3,741
Residential real estate | Acquired credit impaired loans
Changes in allowance for loan losses
Reduction due to loan removals	(132)	(175)	(232)	(237)
Commercial owner occupied real estate loan | Non-acquired loans
Changes in allowance for loan losses
Loans charged-off	(81)		(81)
Recoveries of loans previously charged off	25	98	33	105
Provision for loan losses charged to operations	317	(453)	527	(588)
Consumer real estate | Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off			(807)	(2)
Recoveries of loans previously charged off			55	2
Provision for loan losses charged to operations			752
Consumer real estate | Acquired credit impaired loans
Changes in allowance for loan losses
Reduction due to loan removals	(3)	(4)	(3)	(10)
Commercial and industrial | Non-acquired loans
Changes in allowance for loan losses
Loans charged-off	(59)	(167)	(144)	(189)
Recoveries of loans previously charged off	199	143	214	233
Provision for loan losses charged to operations	238	43	1,153	257
Commercial and industrial | Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off	(764)
Recoveries of loans previously charged off	2	1
Provision for loan losses charged to operations	762	(1)
Commercial and industrial | Acquired credit impaired loans
Changes in allowance for loan losses
Reduction due to loan removals	(16)	(23)	(556)	(54)
Other income producing property | Non-acquired loans
Changes in allowance for loan losses
Loans charged-off		(7)		(7)
Recoveries of loans previously charged off	3	5	11	48
Provision for loan losses charged to operations	17	36	27	(204)
Other income producing property | Acquired non-credit impaired loans
Changes in allowance for loan losses
Recoveries of loans previously charged off		1		1
Provision for loan losses charged to operations		(1)		(1)
Consumer | Non-acquired loans
Changes in allowance for loan losses
Loans charged-off	(1,095)	(797)	(2,074)	(1,510)
Recoveries of loans previously charged off	207	167	410	378
Provision for loan losses charged to operations	1,060	719	1,947	1,314
Consumer | Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off	(127)	(140)
Recoveries of loans previously charged off	46	7
Provision for loan losses charged to operations	81	133
Commercial | Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off			(265)	(214)
Recoveries of loans previously charged off			49	19
Provision for loan losses charged to operations			216	195
Other loans | Non-acquired loans
Changes in allowance for loan losses
Provision for loan losses charged to operations	206	(136)	58	(272)
Construction and land development | Commercial non-owner occupied real estate | Non-acquired loans
Changes in allowance for loan losses
Loans charged-off		(69)	(35)	(474)
Recoveries of loans previously charged off	547	68	989	222
Provision for loan losses charged to operations	(207)	1,098	(688)	1,907
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	(29)	(38)	(82)	(44)
Construction and land development | Commercial | Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off	(106)		(107)
Recoveries of loans previously charged off	6	1	7	2
Provision for loan losses charged to operations	100	(1)	100	(2)
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	7	4	48
Provision for loan losses charged to operations	409	693	680	1,136
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		(3)	(13)	(1)
Other commercial non-owner occupied real estate | Commercial owner occupied real estate loan | Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off			(28)
Provision for loan losses charged to operations			28
Other commercial non-owner occupied real estate | Commercial | Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off	(28)
Provision for loan losses charged to operations	28
Home equity loans | Commercial owner occupied real estate loan | Non-acquired loans
Changes in allowance for loan losses
Loans charged-off			(71)	(224)
Recoveries of loans previously charged off			128	95
Provision for loan losses charged to operations			61	165
Home equity loans | Consumer real estate | Non-acquired loans
Changes in allowance for loan losses
Loans charged-off	(5)	(190)
Recoveries of loans previously charged off	27	21
Provision for loan losses charged to operations	109	(40)
Home equity loans | Consumer real estate | Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off	(158)	(664)	(240)	(664)
Recoveries of loans previously charged off	28	60	79	69
Provision for loan losses charged to operations	130	604	161	595
Consumer Owner Occupied Loans | Consumer real estate | Non-acquired loans
Changes in allowance for loan losses
Loans charged-off		(62)	(4)	(185)
Recoveries of loans previously charged off	41	27	64	76
Provision for loan losses charged to operations	711	496	1,217	858
Consumer Owner Occupied Loans | Consumer real estate | Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off		303
Recoveries of loans previously charged off	5	2
Provision for loan losses charged to operations	$ (5)	$ (305)
Consumer Owner Occupied Loans | Consumer | Acquired non-credit impaired loans
Changes in allowance for loan losses
Loans charged-off			(70)	(10)
Recoveries of loans previously charged off			62	42
Provision for loan losses charged to operations			$ 8	$ (32)