Goodwill and Other Intangible Assets - Estimated Amortization Expense of Finite-Lived Intangible Assets (Details) $ in Thousands	Sep. 30, 2018 USD ($)
Finite-Lived Intangible Assets [Line Items]
2018	$ 7,172
2019	8,078
2020	7,052
2021	5,974
2022	5,054
Core Deposits
Finite-Lived Intangible Assets [Line Items]
2018	7,041
2019	7,947
2020	6,921
2021	5,843
2022	4,923
Customer Relationship Intangible
Finite-Lived Intangible Assets [Line Items]
2018	131
2019	131
2020	131
2021	131
2022	$ 131