Loans - Summary of Covered and Non Covered Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Loans outstanding by class
Loans	$ 3,580,966	$ 3,302,264
Commercial
Loans outstanding by class
Loans	952,407	934,516
Consumer Loans
Loans outstanding by class
Loans	1,742,151	1,609,090
Mortgage Loans
Loans outstanding by class
Loans	638,091	519,748
Commercial | Commercial
Loans outstanding by class
Loans	811,199	784,737
SBA | Commercial
Loans outstanding by class
Loans	141,208	149,779
Construction | Consumer Loans
Loans outstanding by class
Loans	248,317	238,910
Indirect automobile | Consumer Loans
Loans outstanding by class
Loans	1,716,156	1,575,865
Installment | Consumer Loans
Loans outstanding by class
Loans	25,995	33,225
Residential mortgage | Mortgage Loans
Loans outstanding by class
Loans	489,721	386,582
Home equity lines of credit | Mortgage Loans
Loans outstanding by class
Loans	148,370	133,166
Legacy | Non-Covered
Loans outstanding by class
Loans	3,384,399	3,026,749
Legacy | Non-Covered | Commercial
Loans outstanding by class
Loans	808,730	744,896
Legacy | Non-Covered | Consumer Loans
Loans outstanding by class
Loans	1,740,314	1,602,156
Legacy | Non-Covered | Mortgage Loans
Loans outstanding by class
Loans	592,243	453,902
Legacy | Non-Covered | Commercial | Commercial
Loans outstanding by class
Loans	675,544	601,557
Legacy | Non-Covered | SBA | Commercial
Loans outstanding by class
Loans	133,186	143,339
Legacy | Non-Covered | Construction | Consumer Loans
Loans outstanding by class
Loans	243,112	225,795
Legacy | Non-Covered | Indirect automobile | Consumer Loans
Loans outstanding by class
Loans	1,716,156	1,575,865
Legacy | Non-Covered | Installment | Consumer Loans
Loans outstanding by class
Loans	24,158	26,291
Legacy | Non-Covered | Residential mortgage | Mortgage Loans
Loans outstanding by class
Loans	461,194	346,512
Legacy | Non-Covered | Home equity lines of credit | Mortgage Loans
Loans outstanding by class
Loans	131,049	107,390
Acquired | Non-Covered
Loans outstanding by class
Loans	196,567	275,515
Acquired | Non-Covered | Commercial
Loans outstanding by class
Loans	143,677	189,620
Acquired | Non-Covered | Consumer Loans
Loans outstanding by class
Loans	1,837	6,934
Acquired | Non-Covered | Mortgage Loans
Loans outstanding by class
Loans	45,848	65,846
Acquired | Non-Covered | Commercial | Commercial
Loans outstanding by class
Loans	135,655	183,180
Acquired | Non-Covered | SBA | Commercial
Loans outstanding by class
Loans	8,022	6,440
Acquired | Non-Covered | Construction | Consumer Loans
Loans outstanding by class
Loans	5,205	13,115
Acquired | Non-Covered | Indirect automobile | Consumer Loans
Loans outstanding by class
Loans	0	0
Acquired | Non-Covered | Installment | Consumer Loans
Loans outstanding by class
Loans	1,837	6,934
Acquired | Non-Covered | Residential mortgage | Mortgage Loans
Loans outstanding by class
Loans	28,527	40,070
Acquired | Non-Covered | Home equity lines of credit | Mortgage Loans
Loans outstanding by class
Loans	$ 17,321	$ 25,776