Fair Value Measurements - Mortgage Servicing Rights - Summary (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Assets:
Available for sale debt securities, fair value	$ 218,539	$ 218,205
Mortgage servicing rights, fair value	2,875	2,931
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Available for sale debt securities, fair value	2,655	1,952
Mortgage servicing rights, fair value	0	0
Assets, Total	112,270	62,444
Other Observable Inputs (Level 2)
Assets:
Available for sale debt securities, fair value	215,884	216,253
Mortgage servicing rights, fair value	0	0
Assets, Total	224,181	224,470
Significant Unobservable Inputs (Level 3)
Assets:
Available for sale debt securities, fair value	0	0
Mortgage servicing rights, fair value	2,875	2,931
Assets, Total	1,120,583	1,117,934
Recurring
Assets:
Assets, Total	221,427	221,148
Recurring | U.S. Treasury
Assets:
Available for sale debt securities, fair value	2,655	1,952
Recurring | U.S. government and federal agency obligations
Assets:
Available for sale debt securities, fair value	9,515	9,966
Recurring | Government sponsored enterprises
Assets:
Available for sale debt securities, fair value	39,554	43,335
Recurring | Obligations of states and political subdivisions
Assets:
Available for sale debt securities, fair value	38,236	40,386
Recurring | Mortgage-backed securities
Assets:
Available for sale debt securities, fair value	124,243	118,192
Recurring | Other debt securities
Assets:
Available for sale debt securities, fair value	2,999	3,000
Recurring | Bank issued trust preferred securities
Assets:
Available for sale debt securities, fair value	1,337	1,374
Recurring | Equity securities
Assets:
Available for sale debt securities, fair value	13	12
Recurring | Mortgage servicing rights (MSRs)
Assets:
Mortgage servicing rights, fair value	2,875	2,931
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Assets, Total	2,655	1,952
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasury
Assets:
Available for sale debt securities, fair value	2,655	1,952
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. government and federal agency obligations
Assets:
Available for sale debt securities, fair value	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Government sponsored enterprises
Assets:
Available for sale debt securities, fair value	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Obligations of states and political subdivisions
Assets:
Available for sale debt securities, fair value	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mortgage-backed securities
Assets:
Available for sale debt securities, fair value	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other debt securities
Assets:
Available for sale debt securities, fair value	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Bank issued trust preferred securities
Assets:
Available for sale debt securities, fair value	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity securities
Assets:
Available for sale debt securities, fair value	0	0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Mortgage servicing rights (MSRs)
Assets:
Mortgage servicing rights, fair value	0	0
Recurring | Other Observable Inputs (Level 2)
Assets:
Assets, Total	215,897	216,265
Recurring | Other Observable Inputs (Level 2) | U.S. Treasury
Assets:
Available for sale debt securities, fair value	0	0
Recurring | Other Observable Inputs (Level 2) | U.S. government and federal agency obligations
Assets:
Available for sale debt securities, fair value	9,515	9,966
Recurring | Other Observable Inputs (Level 2) | Government sponsored enterprises
Assets:
Available for sale debt securities, fair value	39,554	43,335
Recurring | Other Observable Inputs (Level 2) | Obligations of states and political subdivisions
Assets:
Available for sale debt securities, fair value	38,236	40,386
Recurring | Other Observable Inputs (Level 2) | Mortgage-backed securities
Assets:
Available for sale debt securities, fair value	124,243	118,192
Recurring | Other Observable Inputs (Level 2) | Other debt securities
Assets:
Available for sale debt securities, fair value	2,999	3,000
Recurring | Other Observable Inputs (Level 2) | Bank issued trust preferred securities
Assets:
Available for sale debt securities, fair value	1,337	1,374
Recurring | Other Observable Inputs (Level 2) | Equity securities
Assets:
Available for sale debt securities, fair value	13	12
Recurring | Other Observable Inputs (Level 2) | Mortgage servicing rights (MSRs)
Assets:
Mortgage servicing rights, fair value	0	0
Recurring | Significant Unobservable Inputs (Level 3)
Assets:
Assets, Total	2,875	2,931
Recurring | Significant Unobservable Inputs (Level 3) | U.S. Treasury
Assets:
Available for sale debt securities, fair value	0	0
Recurring | Significant Unobservable Inputs (Level 3) | U.S. government and federal agency obligations
Assets:
Available for sale debt securities, fair value	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Government sponsored enterprises
Assets:
Available for sale debt securities, fair value	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Obligations of states and political subdivisions
Assets:
Available for sale debt securities, fair value	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Mortgage-backed securities
Assets:
Available for sale debt securities, fair value	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Other debt securities
Assets:
Available for sale debt securities, fair value	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Bank issued trust preferred securities
Assets:
Available for sale debt securities, fair value	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Equity securities
Assets:
Available for sale debt securities, fair value	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Mortgage servicing rights (MSRs)
Assets:
Mortgage servicing rights, fair value	$ 2,875	$ 2,931