Summary of Significant Accounting Policies (Policies)	12 Months Ended
Dec. 31, 2015
Accounting Policies [Abstract]
Basis of Presentation	The accompanying consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the U.S. (“GAAP”). The consolidated financial statements include the accounts of ARMOUR Residential REIT, Inc. and its subsidiary. All intercompany accounts and transactions have been eliminated. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Significant estimates affecting the accompanying consolidated financial statements include the valuation of Agency Securities (as defined below), including an assessment of whether other-than-temporary impairment (“OTTI”) exists, and derivative instruments.
Cash	Cash Cash includes cash on deposit with financial institutions. We may maintain deposits in federally insured financial institutions in excess of federally insured limits. However, management believes we are not exposed to significant credit risk due to the financial position and creditworthiness of the depository institutions in which those deposits are held.
Cash Collateral Posted To/By Counterparties	Cash Collateral Posted To/By Counterparties Cash collateral posted to/by counterparties represents cash posted by us to counterparties or posted by counterparties to us as collateral for our interest rate swap contracts (including swaptions and basis swap contracts), Eurodollar Futures Contracts (“Futures Contracts”) and repurchase agreements on our Agency Securities and our Agency Securities purchased or sold on a to-be-announced basis (“TBA Agency Securities”).
Agency Securities, Available for Sale	Agency Securities, Available For Sale We generally intend to hold most of our Agency Securities for extended periods of time. We may, from time to time, sell any of our Agency Securities as part of the overall management of our securities portfolio. Management determines the appropriate classifications of the securities at the time they are acquired and evaluates the appropriateness of such classifications at each balance sheet date. At December 31, 2015 and December 31, 2014, all of our Agency Securities were classified as available for sale securities. Agency Securities classified as available for sale are reported at their estimated fair values with unrealized gains and losses excluded from earnings and reported as part of the consolidated statements of comprehensive income (loss).
Receivables and Payables for Unsettled Sales and Purchases	Receivables and Payables for Unsettled Sales and Purchases We account for purchases and sales of securities on the trade date, including purchases and sales for forward settlement. Receivables and payables for unsettled trades represent the agreed trade price multiplied by the outstanding balance of the securities at the balance sheet date.
Accrued Interest Receivable and Payable	Accrued Interest Receivable and Payable Accrued interest receivable includes interest accrued between payment dates on Agency Securities. Accrued interest payable includes interest payable on our repurchase agreements and may, at certain times, contain interest payable on U.S. Treasury Securities sold short.
Repurchase Agreements	Repurchase Agreements We finance the acquisition of our Agency Securities through the use of repurchase agreements. Our repurchase agreements are secured by our Agency Securities and bear interest rates that have historically moved in close relationship to the Federal Funds Rate and the London Interbank Offered Rate (“LIBOR”). Under these repurchase agreements, we sell Agency Securities to a lender and agree to repurchase the same Agency Securities in the future for a price that is higher than the original sales price. The difference between the sales price that we receive and the repurchase price that we pay represents interest paid to the lender. A repurchase agreement operates as a financing arrangement under which we pledge our Agency Securities as collateral to secure a loan which is equal in value to a specified percentage of the estimated fair value of the pledged collateral. We retain beneficial ownership of the pledged collateral. At the maturity of a repurchase agreement, we are required to repay the loan and concurrently receive back our pledged collateral from the lender or, with the consent of the lender, we may renew such agreement at the then prevailing interest rate. The repurchase agreements may require us to pledge additional assets to the lender in the event the estimated fair value of the existing pledged collateral declines. In addition to the repurchase agreement financing discussed above, at certain times we have entered into reverse repurchase agreements with certain of our repurchase agreement counterparties. Under a typical reverse repurchase agreement, we purchase U.S. Treasury Securities from a borrower in exchange for cash and agree to sell the same securities in the future in exchange for a price that is higher than the original purchase price. The difference between the purchase price originally paid and the sale price represents interest received from the borrower. Reverse repurchase agreement receivables and repurchase agreement liabilities are presented net when they meet certain criteria, including being with the same counterparty, being governed by the same master repurchase agreement (“MRA”), settlement through the same brokerage or clearing account and maturing on the same day.
Obligations to Return Securities Received as Collateral, at Fair Value	Obligations to Return Securities Received as Collateral, at Fair Value At certain times, we also sell to third parties the U.S. Treasury Securities received as collateral for reverse repurchase agreements and recognize the resulting obligation to return said U.S. Treasury Securities as a liability on our consolidated balance sheets. Interest is recorded on the repurchase agreements, reverse repurchase agreements and U.S. Treasury Securities sold short on an accrual basis and presented as interest expense. Both parties to the transaction have the right to make daily margin calls based on changes in the fair value of the collateral received and/or pledged.
Derivatives, at Fair Value	Derivatives, at Fair Value We recognize all derivatives as either assets or liabilities at fair value on our consolidated balance sheets. All changes in the fair values of our derivatives are reflected in our consolidated statements of operations. We designate derivatives as hedges for tax purposes and any unrealized derivative gains or losses would not affect our distributable net taxable income. These transactions include interest rate swap contracts, interest rate swaptions and basis swap contracts. We also may utilize forward contracts for the purchase or sale of TBA Agency Securities. We account for TBA Agency Securities as derivative instruments if it is reasonably possible that we will not take or make physical delivery of the Agency Security upon settlement of the contract. We account for TBA dollar roll transactions as a series of derivative transactions. We may also purchase and sell TBA Agency Securities as a means of investing in and financing Agency Securities (thereby increasing our “at risk” leverage) or as a means of disposing of or reducing our exposure to Agency Securities (thereby reducing our “at risk” leverage). Pursuant to TBA Agency Securities, we agree to purchase or sell, for future delivery, Agency Securities with certain principal and interest terms and certain types of collateral, but the particular Agency Securities to be delivered are not identified until shortly before the TBA settlement date. We may also choose, prior to settlement, to move the settlement of these securities out to a later date by entering into an offsetting short or long position (referred to as a “pair off”), net settling the paired off positions for cash, and simultaneously purchasing or selling a similar TBA Agency Security for a later settlement date. This transaction is commonly referred to as a “dollar roll.” When it is reasonably possible that we will pair off a TBA Agency Security, we account for that contract as a derivative.
Revenue Recognition	Revenue Recognition Interest income is earned and recognized on Agency Securities based on their unpaid principal amounts and their contractual terms. Recognition of interest income commences on the settlement date of the purchase transaction and continues through the settlement date of the sale transaction. Premiums and discounts associated with the purchase of Multi-Family mortgage backed securities (“MBS”), which are generally not subject to prepayment, are amortized or accreted into interest income over the contractual lives of the securities using a level yield method. Premiums and discounts associated with the purchase of other Agency Securities are amortized or accreted into interest income over the actual lives of the securities, reflecting actual prepayments as they occur.
Fair Value of Agency Securities	Fair Value of Agency Securities: We invest in Agency Securities representing interests in or obligations backed by pools of fixed rate, hybrid adjustable rate and adjustable rate mortgage loans. The authoritative literature requires us to classify our investments as either trading, available for sale or held to maturity securities. Management determines the appropriate classifications of the securities at the time they are acquired and evaluates the appropriateness of such classifications at each balance sheet date. We currently classify all of our Agency Securities as available for sale. Agency Securities classified as available for sale are reported at their estimated fair values with unrealized gains and losses excluded from earnings and reported as part of the statements of comprehensive income (loss). Security purchase and sale transactions, including purchase of TBA Agency Securities, are recorded on the trade date to the extent it is probable that we will take or make timely physical delivery of the related securities. Gains or losses realized from the sale of securities are included in income and are determined using the specific identification method.
Impairment of Assets	Impairment of Assets: We evaluate Agency Securities for other than temporary impairment at least on a quarterly basis and more frequently when economic or market concerns warrant such evaluation. We consider an impairment to be other than temporary if we (1) have the intent to sell the Agency Securities, (2) believe it is more likely than not that we will be required to sell the securities before recovery (for example, because of liquidity requirements or contractual obligations) or (3) a credit loss exists. Impairment losses recognized establish a new cost basis for the related Agency Securities.
Comprehensive Income (Loss)	Comprehensive Income (Loss) Comprehensive income (loss) refers to changes in equity during a period from transactions and other events and circumstances from non-owner sources. It includes all changes in equity during a period, except those resulting from investments by owners and distributions to owners.
Reclassification	Reclassification Interest expense amounts on U.S. Treasury Securities sold short have been presented separately in the December 31, 2013 consolidated statements of operations to conform to the current presentation. Gain (loss) on short sale of U.S. Treasury Securities have been adjusted for this change in the consolidated statements of operations and the consolidated statements of cash flows to conform to current presentation. All per share amounts, common shares outstanding and stock-based compensation amounts for all periods presented reflect our one-for-eight reverse stock split (the “Reverse Stock Split”), which was effective July 31, 2015. No other reclassifications have been made to previously reported amounts.
Recent Accounting Pronouncements	In June 2014, the Financial Accounting Standards Board issued ASU 2014-11, Repurchase-to Maturity Transactions, Repurchase Financing, and Disclosures, Transfers and Servicing (Topic 860). We do not have repurchase-to-maturity transactions or repurchase financing arrangements of the type covered by ASU 2014-11, therefore this amendment to the accounting standards will not affect our consolidated balance sheets or statements of operations. The amendment also required certain additional disclosures about repurchase agreements beginning with the second quarter 2015 financial statements. See Note 7 “Repurchase Agreements”.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2015

The accompanying consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the U.S. (“GAAP”). The consolidated financial statements include the accounts of ARMOUR Residential REIT, Inc. and its subsidiary. All intercompany accounts and transactions have been eliminated. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Significant estimates affecting the accompanying consolidated financial statements include the valuation of Agency Securities (as defined below), including an assessment of whether other-than-temporary impairment (“OTTI”) exists, and derivative instruments.

Cash

Cash includes cash on deposit with financial institutions. We may maintain deposits in federally insured financial institutions in excess of federally insured limits. However, management believes we are not exposed to significant credit risk due to the financial position and creditworthiness of the depository institutions in which those deposits are held.

Cash Collateral Posted To/By Counterparties

Cash collateral posted to/by counterparties represents cash posted by us to counterparties or posted by counterparties to us as collateral for our interest rate swap contracts (including swaptions and basis swap contracts), Eurodollar Futures Contracts (“Futures Contracts”) and repurchase agreements on our Agency Securities and our Agency Securities purchased or sold on a to-be-announced basis (“TBA Agency Securities”).

Agency Securities, Available for Sale

Agency Securities, Available For Sale

We generally intend to hold most of our Agency Securities for extended periods of time. We may, from time to time, sell any of our Agency Securities as part of the overall management of our securities portfolio. Management determines the appropriate classifications of the securities at the time they are acquired and evaluates the appropriateness of such classifications at each balance sheet date. At December 31, 2015 and December 31, 2014, all of our Agency Securities were classified as available for sale securities. Agency Securities classified as available for sale are reported at their estimated fair values with unrealized gains and losses excluded from earnings and reported as part of the consolidated statements of comprehensive income (loss).

Receivables and Payables for Unsettled Sales and Purchases

We account for purchases and sales of securities on the trade date, including purchases and sales for forward settlement. Receivables and payables for unsettled trades represent the agreed trade price multiplied by the outstanding balance of the securities at the balance sheet date.

Accrued Interest Receivable and Payable

Accrued interest receivable includes interest accrued between payment dates on Agency Securities. Accrued interest payable includes interest payable on our repurchase agreements and may, at certain times, contain interest payable on U.S. Treasury Securities sold short.

Repurchase Agreements

We finance the acquisition of our Agency Securities through the use of repurchase agreements. Our repurchase agreements are secured by our Agency Securities and bear interest rates that have historically moved in close relationship to the Federal Funds Rate and the London Interbank Offered Rate (“LIBOR”). Under these repurchase agreements, we sell Agency Securities to a lender and agree to repurchase the same Agency Securities in the future for a price that is higher than the original sales price. The difference between the sales price that we receive and the repurchase price that we pay represents interest paid to the lender. A repurchase agreement operates as a financing arrangement under which we pledge our Agency Securities as collateral to secure a loan which is equal in value to a specified percentage of the estimated fair value of the pledged collateral. We retain beneficial ownership of the pledged collateral. At the maturity of a repurchase agreement, we are required to repay the loan and concurrently receive back our pledged collateral from the lender or, with the consent of the lender, we may renew such agreement at the then prevailing interest rate. The repurchase agreements may require us to pledge additional assets to the lender in the event the estimated fair value of the existing pledged collateral declines.

In addition to the repurchase agreement financing discussed above, at certain times we have entered into reverse repurchase agreements with certain of our repurchase agreement counterparties. Under a typical reverse repurchase agreement, we purchase U.S. Treasury Securities from a borrower in exchange for cash and agree to sell the same securities in the future in exchange for a price that is higher than the original purchase price. The difference between the purchase price originally paid and the sale price represents interest received from the borrower. Reverse repurchase agreement receivables and repurchase agreement liabilities are presented net when they meet certain criteria, including being with the same counterparty, being governed by the same master repurchase agreement (“MRA”), settlement through the same brokerage or clearing account and maturing on the same day.

Obligations to Return Securities Received as Collateral, at Fair Value

At certain times, we also sell to third parties the U.S. Treasury Securities received as collateral for reverse repurchase agreements and recognize the resulting obligation to return said U.S. Treasury Securities as a liability on our consolidated balance sheets. Interest is recorded on the repurchase agreements, reverse repurchase agreements and U.S. Treasury Securities sold short on an accrual basis and presented as interest expense. Both parties to the transaction have the right to make daily margin calls based on changes in the fair value of the collateral received and/or pledged.

Derivatives, at Fair Value

We recognize all derivatives as either assets or liabilities at fair value on our consolidated balance sheets. All changes in the fair values of our derivatives are reflected in our consolidated statements of operations. We designate derivatives as hedges for tax purposes and any unrealized derivative gains or losses would not affect our distributable net taxable income. These transactions include interest rate swap contracts, interest rate swaptions and basis swap contracts. We also may utilize forward contracts for the purchase or sale of TBA Agency Securities. We account for TBA Agency Securities as derivative instruments if it is reasonably possible that we will not take or make physical delivery of the Agency Security upon settlement of the contract. We account for TBA dollar roll transactions as a series of derivative transactions.

We may also purchase and sell TBA Agency Securities as a means of investing in and financing Agency Securities (thereby increasing our “at risk” leverage) or as a means of disposing of or reducing our exposure to Agency Securities (thereby reducing our “at risk” leverage). Pursuant to TBA Agency Securities, we agree to purchase or sell, for future delivery, Agency Securities with certain principal and interest terms and certain types of collateral, but the particular Agency Securities to be delivered are not identified until shortly before the TBA settlement date. We may also choose, prior to settlement, to move the settlement of these securities out to a later date by entering into an offsetting short or long position (referred to as a “pair off”), net settling the paired off positions for cash, and simultaneously purchasing or selling a similar TBA Agency Security for a later settlement date. This transaction is commonly referred to as a “dollar roll.” When it is reasonably possible that we will pair off a TBA Agency Security, we account for that contract as a derivative.

Revenue Recognition

Interest income is earned and recognized on Agency Securities based on their unpaid principal amounts and their contractual terms. Recognition of interest income commences on the settlement date of the purchase transaction and continues through the settlement date of the sale transaction. Premiums and discounts associated with the purchase of Multi-Family mortgage backed securities (“MBS”), which are generally not subject to prepayment, are amortized or accreted into interest income over the contractual lives of the securities using a level yield method. Premiums and discounts associated with the purchase of other Agency Securities are amortized or accreted into interest income over the actual lives of the securities, reflecting actual prepayments as they occur.

Fair Value of Agency Securities

Fair Value of Agency Securities: We invest in Agency Securities representing interests in or obligations backed by pools of fixed rate, hybrid adjustable rate and adjustable rate mortgage loans. The authoritative literature requires us to classify our investments as either trading, available for sale or held to maturity securities. Management determines the appropriate classifications of the securities at the time they are acquired and evaluates the appropriateness of such classifications at each balance sheet date. We currently classify all of our Agency Securities as available for sale. Agency Securities classified as available for sale are reported at their estimated fair values with unrealized gains and losses excluded from earnings and reported as part of the statements of comprehensive income (loss).

Security purchase and sale transactions, including purchase of TBA Agency Securities, are recorded on the trade date to the extent it is probable that we will take or make timely physical delivery of the related securities. Gains or losses realized from the sale of securities are included in income and are determined using the specific identification method.

Impairment of Assets

Impairment of Assets: We evaluate Agency Securities for other than temporary impairment at least on a quarterly basis and more frequently when economic or market concerns warrant such evaluation. We consider an impairment to be other than temporary if we (1) have the intent to sell the Agency Securities, (2) believe it is more likely than not that we will be required to sell the securities before recovery (for example, because of liquidity requirements or contractual obligations) or (3) a credit loss exists. Impairment losses recognized establish a new cost basis for the related Agency Securities.

Comprehensive Income (Loss)

Comprehensive income (loss) refers to changes in equity during a period from transactions and other events and circumstances from non-owner sources. It includes all changes in equity during a period, except those resulting from investments by owners and distributions to owners.

Reclassification

Interest expense amounts on U.S. Treasury Securities sold short have been presented separately in the December 31, 2013 consolidated statements of operations to conform to the current presentation. Gain (loss) on short sale of U.S. Treasury Securities have been adjusted for this change in the consolidated statements of operations and the consolidated statements of cash flows to conform to current presentation. All per share amounts, common shares outstanding and stock-based compensation amounts for all periods presented reflect our one-for-eight reverse stock split (the “Reverse Stock Split”), which was effective July 31, 2015.

No other reclassifications have been made to previously reported amounts.

Recent Accounting Pronouncements

In June 2014, the Financial Accounting Standards Board issued ASU 2014-11, Repurchase-to Maturity Transactions, Repurchase Financing, and Disclosures, Transfers and Servicing (Topic 860). We do not have repurchase-to-maturity transactions or repurchase financing arrangements of the type covered by ASU 2014-11, therefore this amendment to the accounting standards will not affect our consolidated balance sheets or statements of operations. The amendment also required certain additional disclosures about repurchase agreements beginning with the second quarter 2015 financial statements. See Note 7 “Repurchase Agreements”.