Borrowings - Components (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Borrowings
Total borrowings	$ 56,612	$ 57,006
Stonegate
Borrowings
Maximum investment by Stonegate in the Company's subordinated debt	$ 30,000
Bank
Borrowings
Ownership in subsidiary (as a percent)	100.00%
Line of credit
Borrowings
Total borrowings	$ 25,000	$ 25,000
Maximum borrowing capacity	$ 25,000
Tier 1 Leverage Ratio (as a percent)	8.00%
Line of credit | LIBOR
Borrowings
Basis spread on variable rate (as a percent)		2.485%
Line of credit | Minimum | LIBOR
Borrowings
Basis spread on variable rate (as a percent)	1.85%
Line of credit | Maximum | LIBOR
Borrowings
Basis spread on variable rate (as a percent)	3.23%
Short-term subordinated debt
Borrowings
Total borrowings	$ 30,000	$ 30,000
Additional interest as a percentage of earnings	49.00%
Short-term subordinated debt | LIBOR
Borrowings
Basis spread on variable rate (as a percent)	3.50%
Short-term subordinated debt | Bank | NMF
Borrowings
Shares of NMF pledged as consideration for investment by Stonegate in the subordinated debt of the Company (as a percent)	100.00%
FHLB advances
Borrowings
Total borrowings	$ 1,612	2,006
Mortgage loans pledged as collateral	74,400	64,300
Available for sale securities and securities purchased under agreements to resell pledged as collateral	$ 407,700	$ 320,100
FHLB advances | Minimum
Borrowings
FHLB advances interest rate	2.27%	2.00%
FHLB advances | Maximum
Borrowings
FHLB advances interest rate	4.74%	4.74%