Other Noninterest Income and Expense - Summary of Noninterest Expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Other Noninterest Income And Expense [Line Items]
Total other noninterest expenses	$ 4,753	$ 4,039
Customer bank card processing
Other Noninterest Income And Expense [Line Items]
Total other noninterest expenses	591	516
Subscriptions
Other Noninterest Income And Expense [Line Items]
Total other noninterest expenses	481	422
Telephone and data communications
Other Noninterest Income And Expense [Line Items]
Total other noninterest expenses	476	465
Pennsylvania shares and use taxes
Other Noninterest Income And Expense [Line Items]
Total other noninterest expenses	371	292
Internet banking and bill pay
Other Noninterest Income And Expense [Line Items]
Total other noninterest expenses	365	346
Travel, entertainment and conferences
Other Noninterest Income And Expense [Line Items]
Total other noninterest expenses	352	330
Correspondent bank and courier fees
Other Noninterest Income And Expense [Line Items]
Total other noninterest expenses	339	265
Printing and supplies
Other Noninterest Income And Expense [Line Items]
Total other noninterest expenses	291	362
Marketing and advertising
Other Noninterest Income And Expense [Line Items]
Total other noninterest expenses	287	291
Charitable contributions
Other Noninterest Income And Expense [Line Items]
Total other noninterest expenses	181	180
Regulatory examinations
Other Noninterest Income And Expense [Line Items]
Total other noninterest expenses	185	177
Postage and freight
Other Noninterest Income And Expense [Line Items]
Total other noninterest expenses	130	131
Memberships and dues
Other Noninterest Income And Expense [Line Items]
Total other noninterest expenses	99	94
Penalty on prepayment of FHLB advance
Other Noninterest Income And Expense [Line Items]
Total other noninterest expenses	0	71
Other
Other Noninterest Income And Expense [Line Items]
Total other noninterest expenses	$ 605	$ 97