Summary of Significant Accounting Policies (Narrative) (Details)	3 Months Ended	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2019 USD ($) Loan_Production_Offices Loan Operation_centers branches	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jan. 01, 2019 USD ($)	Mar. 31, 2018 USD ($)
Property, Plant and Equipment [Line Items]
Reclassification from AOCI to retained earnings			$ 19,000
Number of operation centers | Operation_centers		2
Number of LPOs | Loan_Production_Offices		4
Increase in assets as a result of business combinations						$ 1,600,000,000
Trading securities	$ 0	$ 0	0	$ 0
Loans held for sale		$ 0	0
Number of mortgage loans sold | Loan		0
Equity securities		$ 4,669,000	4,428,000
Right of use assets - operating leases		8,382,000
Lease liabilities - operating leases		8,495,000
Reclassification due to Accounting Standard Update (ASU 2018-02)	$ (196,000)	$ 0	$ 19,000	$ 196,000
Accounting Standards Update 2016-02 [Member]
Property, Plant and Equipment [Line Items]
Right of use assets - operating leases					$ 8,000,000
Lease liabilities - operating leases					$ 11,000,000
Maryland and Virginia [Member]
Property, Plant and Equipment [Line Items]
Number of branches | branches		12
Waldrof [Member]
Property, Plant and Equipment [Line Items]
Number of branches | branches		2
Leonardtown, La Plata [Member]
Property, Plant and Equipment [Line Items]
Number of branches | branches		2
Building and Building Improvements [Member] | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life		50 years
Building and Building Improvements [Member] | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life		10 years
Furniture and Fixtures [Member] | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life		15 years
Furniture and Fixtures [Member] | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life		3 years
Automobiles [Member] | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life		5 years
Automobiles [Member] | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life		4 years