Summary of Significant Accounting Policies (Policies)	9 Months Ended
Summary of Significant Accounting Policies (Policies)	Sep. 30, 2019
Summary of Significant Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accounting and reporting policies of Severn Bancorp, Inc. and subsidiaries (the “Company”) conform to accounting principles generally accepted in the United States of America (“U.S.”) (“GAAP”) and prevailing practices within the financial services industry for interim financial information and Rule 8‑01 of Regulation S-X. Accordingly, they do not include all of the information and notes required for complete financial statements and prevailing practices within the banking industry. In the opinion of management, all adjustments (comprising only of those of a normal recurring nature) necessary for a fair presentation of the results of operations for the interim periods presented have been made. The results of operations for the three and nine months ended September 30, 2019 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2019 or any other interim or future period. Events occurring after the date of the financial statements up to the date the financial statements were available to be issued were considered in the preparation of the consolidated financial statements. These statements should be read in conjunction with the financial statements and accompanying notes included in the Company’s 2018 Annual Report on Form 10‑K as filed with the Securities and Exchange Commission (“SEC”).
Principles of Consolidation	Principles of Consolidation The unaudited consolidated financial statements include the accounts of Severn Bancorp, Inc., and its wholly-owned subsidiaries, Mid-Maryland Title Company, Inc., SBI Mortgage Company, and Severn Savings Bank, FSB (the “Bank”), along with the Bank’s subsidiaries, Louis Hyatt, Inc., Homeowners Title and Escrow Corporation, Severn Financial Services Corporation, SSB Realty Holdings, LLC, SSB Realty Holdings II, LLC, and HS West, LLC. Also included are the accounts of SBI Mortgage Company’s subsidiary, Crownsville Development Corporation, and its subsidiary, Crownsville Holdings I, LLC. All intercompany accounts and transactions have been eliminated in the accompanying consolidated financial statements.
Use of Estimates	Use of Estimates The preparation of the financial statements requires management to exercise significant judgment or discretion or make significant assumptions and estimates based on the information available that have, or could have, a material impact on the carrying value of certain assets or on income. These estimates and assumptions affect the reported amounts of assets and liabilities at the date of the financial statements and the reported amounts of income and expenses during the periods presented. The accounting policies we view as critical are those relating to the allowance for loan losses (“Allowance”), the valuation of securities, the valuation of real estate acquired through foreclosure, and the valuation of deferred tax assets and liabilities.
Cash Flows	Cash Flows We consider all highly liquid securities with original maturities of three months or less to be cash equivalents. For reporting purposes, assets grouped in the Consolidated Statements of Financial Condition under the captions “Cash and due from banks” and “Federal funds sold and interest-bearing deposits in other banks” are considered cash or cash equivalents. For financial statement purposes, these assets are carried at cost. Federal funds sold and interest-bearing deposits in other banks generally have overnight maturities and are in excess of amounts that would be recoverable under Federal Deposit Insurance Corporation (“FDIC”) insurance.
Reclassifications	Reclassifications Certain reclassifications have been made to amounts previously reported to conform to current period presentation.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Pronouncements Adopted In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016‑02, Leases, which requires a lessee to recognize the assets and liabilities that arise from all leases with a term greater than 12 months. The core principle requires the lessee to recognize a liability to make lease payments and a right-of-use (“ROU”) asset. The accounting applied by the lessor is relatively unchanged. The ASU also requires expanded qualitative and quantitative disclosures. For public business entities, the guidance was effective for interim and annual reporting periods beginning after December 15, 2018 and mandated a modified retrospective transition for all entities. We adopted this standard using the option to apply the transition provisions of the new standard at the adoption date instead of the earliest period presented as provided in ASU 2018-11. Additionally, we elected to apply all practical expedients as provided in ASU 2016-02, with the exception of the hindsight practical expedient which was not elected. As a result of the adoption of this standard, effective January 1, 2019, we recognized both an ROU asset and a lease liability of $2.7 million to be recorded in other assets and other liabilities, respectively, on the balance sheet. The lease liability represented the present value of the future payments on five leased properties and six leased pieces of equipment within the Company’s footprint, while the ROU asset reflected the lease liability adjusted for deferred rent balances of the respective properties as of the adoption date of January 1, 2019. The Company expects its regulatory capital ratios to remain above the thresholds necessary to be classified as a “well capitalized” institution. In March 2017, FASB issued ASU No. 2017‑08, Receivables - Nonrefundable Fees and Other costs, which provided guidance that called for the shortening of the amortization period for certain callable debt securities held at a premium. The standard was effective for interim and annual reporting periods beginning after December 15, 2018. The adoption of ASU No. 2017‑08 did not have a material impact on our financial position, results of operations, or cash flows. In February 2018, FASB issued ASU No. 2018-02, Reclassification of Certain Tax Effects From Accumulated Other Comprehensive Income, which allowed a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act. The ASU was effective for all entities for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. The adoption of ASU No. 2018-02 did not have a material impact on its financial position, results of operations, or cash flows. Pronouncements Issued In September 2016, FASB issued ASU No. 2016‑13, Financial Instruments – Credit Losses, which sets forth a current expected credit loss (“CECL”) model which requires the Company to measure all expected credit losses for financial instruments held at the reporting date based on historical experience, current conditions, and reasonable supportable forecasts. This replaces the existing incurred loss model and is applicable to the measurement of credit losses on financial assets measured at amortized cost and applies to some off-balance sheet credit exposures. This ASU is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. In July 2019, the FASB issued a proposal to delay the implementation for smaller reporting companies such as us until January 2023. In October, 2019, that proposal was finalized. We have contracted with a third party vendor to assist in the transition to CECL. The Bank has purchased the third party vendor’s CECL software and has separately contracted with their advisory services group to help with the installation and transition. As the Bank has been using other software of this specific vendor, they have access to the Bank’s historical data. The third party vendor has been analyzing the Bank’s data, and the Bank has been updating the data and the process by which data will be transferred to the third party vendor, so that they have all of the information necessary for CECL calculations. This process is almost complete. The third party vendor has also begun determining which economic factors are most directly responsible for Bank’s historical losses. They have also started to recommend pools to be used for CECL calculations, and appropriate methods (as proscribed by CECL) to calculate the reserve for the various pools. As the third party vendor has many financial institution clients, they will be able to provide peer group data to the extent the Bank’s data is not sufficient to make the many determinations required under CECL. Although the implementation of CECL has been delayed, the Bank will continue with the implementation at a pace to ensure that we will be in position to completely transition to CECL by the required date. While we are currently in the process of evaluating the impact of the amended guidance on our Consolidated Financial Statements, it is quite possible that the Allowance will increase upon adoption given that the Allowance will be required to cover the full remaining expected life of the portfolio upon adoption, rather than the incurred loss model under current GAAP. The extent of this increase is still being evaluated and will depend on economic conditions and the composition of our loan and lease portfolio at the time of adoption.