Fair Value Measurements - Financial Assets Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	$ 321,337	$ 346,502
Federal agencies and GSEs
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	112,127	104,054
Mortgage-backed and CMOs
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	105,316	79,493
State and municipal
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	93,626	147,515
Corporate
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	8,062	13,492
Equity securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	2,206	1,948
Level 1
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	0	0
Level 2
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	321,337	346,502
Level 3
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	0	0
Recurring
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	321,337	346,502
Recurring | Federal agencies and GSEs
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	112,127	104,054
Recurring | Mortgage-backed and CMOs
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	105,316	79,493
Recurring | State and municipal
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	93,626	147,515
Recurring | Corporate
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	8,062	13,492
Recurring | Equity securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	2,206	1,948
Recurring | Level 1
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	0	0
Recurring | Level 1 | Federal agencies and GSEs
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	0	0
Recurring | Level 1 | Mortgage-backed and CMOs
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	0	0
Recurring | Level 1 | State and municipal
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	0	0
Recurring | Level 1 | Corporate
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	0	0
Recurring | Level 1 | Equity securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	0	0
Recurring | Level 2
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	321,337	346,502
Recurring | Level 2 | Federal agencies and GSEs
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	112,127	104,054
Recurring | Level 2 | Mortgage-backed and CMOs
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	105,316	79,493
Recurring | Level 2 | State and municipal
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	93,626	147,515
Recurring | Level 2 | Corporate
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	8,062	13,492
Recurring | Level 2 | Equity securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	2,206	1,948
Recurring | Level 3
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	0	0
Recurring | Level 3 | Federal agencies and GSEs
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	0	0
Recurring | Level 3 | Mortgage-backed and CMOs
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	0	0
Recurring | Level 3 | State and municipal
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	0	0
Recurring | Level 3 | Corporate
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	0	0
Recurring | Level 3 | Equity securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Fair Value	$ 0	$ 0