Commitments - Summary of Financial Instrument Commitments (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fixed
Financial instrument commitments
Financial instrument commitments	$ 315	$ 126
Loan commitments	68,996	71,016
Fixed | Borrower
Financial instrument commitments
Financial instrument commitments	220	126
Fixed | Borrower | Financial standby
Financial instrument commitments
Financial instrument commitments	137	60
Fixed | Borrower | Performance standby
Financial instrument commitments
Financial instrument commitments	83	66
Fixed | Nonborrower
Financial instrument commitments
Financial instrument commitments	95
Fixed | Nonborrower | Performance standby
Financial instrument commitments
Financial instrument commitments	95
Variable
Financial instrument commitments
Financial instrument commitments	13,196	11,544
Loan commitments	270,989	197,909
Variable | Borrower
Financial instrument commitments
Financial instrument commitments	12,672	10,969
Variable | Borrower | Financial standby
Financial instrument commitments
Financial instrument commitments	4,047	3,572
Variable | Borrower | Commercial standby
Financial instrument commitments
Financial instrument commitments	126	47
Variable | Borrower | Performance standby
Financial instrument commitments
Financial instrument commitments	8,499	7,350
Variable | Nonborrower
Financial instrument commitments
Financial instrument commitments	524	575
Variable | Nonborrower | Performance standby
Financial instrument commitments
Financial instrument commitments	524	575
Total.
Financial instrument commitments
Financial instrument commitments	13,511	11,670
Loan commitments	339,985	268,925
Total. | Borrower
Financial instrument commitments
Financial instrument commitments	12,892	11,095
Total. | Borrower | Financial standby
Financial instrument commitments
Financial instrument commitments	4,184	3,632
Total. | Borrower | Commercial standby
Financial instrument commitments
Financial instrument commitments	126	47
Total. | Borrower | Performance standby
Financial instrument commitments
Financial instrument commitments	8,582	7,416
Total. | Nonborrower
Financial instrument commitments
Financial instrument commitments	619	575
Total. | Nonborrower | Performance standby
Financial instrument commitments
Financial instrument commitments	$ 619	$ 575