Subordinated Debentures (Details) $ / shares in Units, $ in Thousands		9 Months Ended	12 Months Ended
	Nov. 15, 2008 USD ($) $ / shares shares	Sep. 30, 2016 USD ($)	Dec. 31, 2017 USD ($) Quarter $ / shares	Dec. 31, 2015 USD ($) Quarter	Dec. 31, 2016 USD ($)
Debt Instrument [Line Items]
Private placement offering price (per unit) | $ / shares			$ 100
Subordinated note outstanding			$ 20,619		$ 20,619
Series A Preferred Stock [Member]
Debt Instrument [Line Items]
Number of private placement offering | shares	70
Private placement offering price (per unit) | $ / shares	$ 100,000
Gross proceeds of private placement	$ 7,000
Number of shares issued in private placement for each unit (in shares) | shares	6,250
Aggregate preferred stock outstanding	$ 3,500		4		$ 4
Junior Subordinated Debt Securities [Member]
Debt Instrument [Line Items]
Principal amount of debt			$ 20,600
Maturity date			Jan. 07, 2035
Basis spread on variable rate			2.00%
Permitted number of consecutive quarterly interest payment deferment period | Quarter			20
Number of quarters of interest and the cumulative amount of interest in arrears not paid | Quarter				15
Interest on unpaid interest				$ 1,900
Subordinated note outstanding	3,500
Payment for subordinated notes outstanding		$ 3,500
Annual interest rate on subordinated notes		8.00%
Subordinated Note, original principal amount	$ 50
Junior Subordinated Debt Securities [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Term of variable rate			3 months
Severn Capital Trust I [Member]
Debt Instrument [Line Items]
Common equity owned			100.00%