ACCOUNTING POLICIES (Policies)	12 Months Ended
Dec. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The consolidated financial statements include the accounts of Capstead Mortgage Corporation and its wholly-owned and majority-owned subsidiaries over which it exercises control. Pursuant to variable interest entity (“VIE”) accounting principles, Capstead considers for consolidation any VIE in which it holds an interest. Intercompany balances and transactions are eliminated.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update No. 2016-02, Leases (“ASU 2016-02”) which requires entities who are lessees to recognize a right-of-use asset and a lease liability arising from those leases on the balance sheet. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. The Company adopted ASU 2016-02 on January 1, 2019, which had no material effect on the Company’s results of operations, financial condition and cash flows. In June 2016, the FASB issued Accounting Standards Update No. 2016-13, Financial Instruments – Credit Losses (“ASU 2016-13”) which replaces the incurred loss impairment methodology in current GAAP to a methodology that better reflects expected credit losses. For financial instruments carried at amortized cost, impairment will be measured as a current estimate of expected lifetime credit losses. For available-for-sale debt securities in which changes in fair value are recorded in accumulated other comprehensive income, the FASB made targeted improvements eliminating the write-down of available-for-sale securities under the “other-than-temporarily” impaired model with an allowance for credit losses model. ASU 2016-13 is effective for fiscal years beginning after December 15, 2019 and interim periods within those fiscal years. The Company adopted ASU 2016-13 on January 1, 2020 which, primarily due to the limited credit risk on Agency Securities as discussed in NOTE 1, had no material effect on the Company’s results of operations, financial condition and cash flows.
Use of Estimates	Use of Estimates Fair values of nearly all financial instruments held by the Company are estimated based on a market approach using available market information and appropriate valuation methodologies (Level Two Inputs); however, judgment is required in interpreting market data to develop these estimates. Fair values fluctuate on a daily basis and are influenced by changes in, and market expectations for changes in, interest rates, market liquidity conditions and levels of mortgage prepayments, as well as other factors. Accordingly, estimates of fair value are as of the balance sheet dates and are not necessarily indicative of the amounts that could be realized in a current market exchange. The use of different market assumptions and estimation methodologies may have a material effect on estimated fair values. Judgment is also exercised in making impairment conclusions and estimating impairment charges. Amortization of investment premiums on financial assets is based in part on estimates of future levels of mortgage prepayments. Estimates are influenced by changes in, and market expectations for changes in, interest rates, market liquidity conditions, actual levels of mortgage prepayments and other factors. Judgment is required in developing these estimates, however the actual level of mortgage prepayments for a given accounting period is the single largest determinant in amortizing investment premiums.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents include unrestricted cash on hand and highly liquid investments with original maturities of three months or less when purchased.
Financial Assets	Financial Assets Capstead’s financial assets consist almost exclusively of Agency Securities classified as available-for-sale and carried at fair value with net unrealized gains and losses reported as a separate component of Accumulated other comprehensive income (loss). Loans classified as held for investment or mortgage securities classified as held-to-maturity are recorded at amortized cost (unpaid principal balance, adjusted for unamortized investment premiums and discounts). Interest is recorded as income when earned. Investment premiums and discounts are recognized as adjustments to interest income by the interest method over the expected life of the related financial assets. Realized gains and losses from any financial asset sales are recorded as a component of Other (expense) income. The specific identification method is used to determine the cost of financial assets sold. Financial assets are reviewed for potential impairment at each balance sheet date. Other-than-temporary impairments of investments in mortgage securities can occur with changes in the Company’s intent or ability to hold the mortgage securities until any declines in fair value are recovered and as a result of adverse changes in the financial condition of the issuer(s) such that a full recovery of cost basis is no longer expected. The amount of any such other-than-temporary impairment for an investment in a mortgage security is measured by comparing the recorded amount of the security to its fair value. Other-than-temporary impairment charges would be recorded as a component of Other (expense) income if the impairment results from changes in the Company’s intent or ability to hold the securities. Should other-than-temporary impairment arise as a result of adverse changes in the financial condition of the issuer(s) without changing the Company’s intent and ability to hold the securities, the credit component of the impairment would be recorded as a component of Other (expense) income with any remainder recorded as a component of Other comprehensive income (loss).
Borrowings	Borrowings Secured borrowings in the form of repurchase arrangements create exposure to the potential for failure on the part of counterparties to honor their commitment to return pledged collateral. In the event of a default by a repurchase arrangement counterparty, the Company may have difficulty recovering its collateral. To mitigate this risk, the Company monitors the creditworthiness of its counterparties and manages its exposure to any single counterparty. Capstead’s borrowings are carried at their principal balances outstanding net of related debt issuance costs and debt discounts, if applicable. Debt issuance costs associated with Unsecured borrowings are recognized as adjustments to interest expense by the interest method over the term of these borrowings.
Derivative Financial Instruments ("Derivatives")	Derivative Financial Instruments (“Derivatives”) Derivatives used by Capstead for risk management purposes are carried at fair value as assets or liabilities. The accounting for changes in fair value of Derivatives held depends on whether it has been designated as a hedge for accounting purposes, as well as the type of hedging relationship identified. Capstead may designate any Derivatives held as cash flow hedges related to a designated portion of its current and anticipated future borrowings. To qualify as a cash flow hedge, at the inception of the hedge relationship the Company must document that the hedge relationship is anticipated to be highly effective and monitor ongoing effectiveness on at least a quarterly basis. As long as the hedge relationship remains effective, the change in fair value of the Derivatives are recorded in Accumulated other comprehensive income (loss). Changes in fair value of Derivatives not held as accounting hedges, if any, or for which the hedge relationship is no longer considered highly effective, are recorded in earnings as a component of Other (expense) income. On March 1, 2019 the Company discontinued its use of hedge accounting on its interest rate swaps related to Secured borrowings, while retaining hedge accounting for swaps related to Unsecured borrowings. The Company uses Derivatives primarily in the form of interest rate swap agreements to hedge the variability in borrowing rates on its secured and unsecured borrowings. If designated as accounting hedges, related fixed interest payments and variable interest receipts are recorded as an adjustment to interest expense on the related designated borrowings. If not designated as accounting hedges, fixed interest payments and variable interest receipts are recorded as a component of Other (expense) income. For Derivatives initially designated as accounting hedges and subsequently de-designated, unrealized gain or loss included in Accumulated other comprehensive income (loss) at the time of de-designation is amortized as an adjustment to interest expense on the related borrowings over the remaining term of the Derivatives. Derivatives create exposure to credit risk related to the potential for failure on the part of counterparties to honor their commitments. In addition, the Company is required to post collateral based on any declines in the market value of the Derivatives. In the event of default by a counterparty, the Company may have difficulty recovering its collateral and may not receive payments provided for under the terms of the Derivatives. To mitigate this risk, the Company uses only well-established commercial banks as counterparties and, pursuant to regulatory changes implemented in 2013, most Derivatives held at December 31, 2019 were entered into through Derivative exchanges established in part to mitigate credit risk. Cash collateral receivable from derivative counterparties, when present, represents cash remitted to swap counterparties to meet initial and ongoing margin requirements that are based on the fair value of these Derivatives, including related interest receivable or payable under the terms of the agreements. The Company may also remit mortgage securities to certain of its swap counterparties to meet ongoing margin requirements. Such mortgage securities, if any, are included in Residential mortgage investments. Similarly, Cash collateral payable to derivative counterparties, when present, represents cash received from counterparties to meet margin call requirements. For presentation purposes, the Company does not offset individual counterparty collateral receivables (or payables) with the recorded fair value of related interest rate swap agreements pursuant to master netting arrangements. In addition, gross unrealized gains on Derivatives (recorded as assets) are stated separately from gross unrealized losses (recorded as liabilities) without regard to counterparty. Certain cash margin amounts are presented on a net basis against the fair value of related Derivatives.
Long-term Incentive Compensation	Long-term Incentive Compensation Capstead provides its employees and its directors with long-term incentive compensation in the form of equity-based awards. Equity-based compensation costs are initially measured at the estimated fair value of the awards on the grant date developed using appropriate valuation methodologies. Valuation methodologies used and subsequent expense recognition is dependent upon each award’s service and performance conditions, the latter also referred to as performance metrics. Capstead has elected not to estimate future award forfeitures when valuing equity-based awards and will adjust compensation costs as actual forfeitures occur. Compensation costs for equity-based awards subject only to service conditions are measured at the closing stock price on the dates of grant and are recognized as expense on a straight-line basis over the requisite service periods for the awards, as adjusted for any forfeitures. Compensation costs for components of equity-based awards subject to nonmarket-based performance metrics (i.e. metrics not predicated on changes in the Company’s stock price), are measured at the closing stock price on the dates of grant, adjusted for the probability of achieving benchmarks included in the performance metrics. These initial cost estimates are recognized as expense over the requisite performance periods, adjusted for subsequent changes in performance estimates. Compensation costs for components of equity-based awards subject to market-based performance metrics are measured at the dates of grant using Monte Carlo simulations which incorporate into the valuations the inherent uncertainty regarding achieving the market-based performance metrics. These initial valuation amounts are recognized as expense over the requisite performance periods, subject to adjustments only for actual forfeitures.
Income Taxes	Income Taxes Capstead Mortgage Corporation and its qualified REIT subsidiaries (“Capstead REIT”) have elected to be taxed as a REIT. As a result, Capstead REIT is not taxed on taxable income distributed to stockholders if certain REIT qualification tests are met. Capstead’s policy is to distribute 100% of its taxable income, after application of available tax attributes, within the time limits prescribed by the Internal Revenue Code (the “Code”), which may extend into the subsequent taxable year. The Company may find it advantageous from time to time to elect taxable REIT subsidiary status for certain of its subsidiaries in which case taxable income of any such subsidiary would be subject to federal and, where applicable, state or local income taxes. Any such income taxes are accounted for using the liability method. Related deferred income tax assets and liabilities are determined based on differences between the financial reporting and tax bases of assets and liabilities and are measured using enacted tax rates and laws that will be in effect when the differences are expected to reverse. The Company has not recognized any liabilities for unrecognized tax benefits using a “more likely than not” threshold for the recognition and measurement of the financial statement effects of tax positions taken on a tax return filing. Should any such liabilities be recognized in future periods, the Company will record related interest and penalties in Other general and administrative expense.
Dividend Classification	Dividend Classification The tax and financial reporting classification of dividends can differ primarily as a result of differences between taxable income attributable to a particular tax year and that year’s Net income (loss), the amount and timing of dividends paid relative to taxable income and how such taxable income is allocated to dividends paid.

ACCOUNTING POLICIES (Policies)

12 Months Ended

Dec. 31, 2019

The consolidated financial statements include the accounts of Capstead Mortgage Corporation and its wholly-owned and majority-owned subsidiaries over which it exercises control. Pursuant to variable interest entity (“VIE”) accounting principles, Capstead considers for consolidation any VIE in which it holds an interest. Intercompany balances and transactions are eliminated.

Recent Accounting Pronouncements

In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update No. 2016-02, Leases (“ASU 2016-02”) which requires entities who are lessees to recognize a right-of-use asset and a lease liability arising from those leases on the balance sheet. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. The Company adopted ASU 2016-02 on January 1, 2019, which had no material effect on the Company’s results of operations, financial condition and cash flows.

In June 2016, the FASB issued Accounting Standards Update No. 2016-13, Financial Instruments – Credit Losses (“ASU 2016-13”) which replaces the incurred loss impairment methodology in current GAAP to a methodology that better reflects expected credit losses. For financial instruments carried at amortized cost, impairment will be measured as a current estimate of expected lifetime credit losses. For available-for-sale debt securities in which changes in fair value are recorded in accumulated other comprehensive income, the FASB made targeted improvements eliminating the write-down of available-for-sale securities under the “other-than-temporarily” impaired model with an allowance for credit losses model. ASU 2016-13 is effective for fiscal years beginning after December 15, 2019 and interim periods within those fiscal years. The Company adopted ASU 2016-13 on January 1, 2020 which, primarily due to the limited credit risk on Agency Securities as discussed in NOTE 1, had no material effect on the Company’s results of operations, financial condition and cash flows.

Use of Estimates

Fair values of nearly all financial instruments held by the Company are estimated based on a market approach using available market information and appropriate valuation methodologies (Level Two Inputs); however, judgment is required in interpreting market data to develop these estimates. Fair values fluctuate on a daily basis and are influenced by changes in, and market expectations for changes in, interest rates, market liquidity conditions and levels of mortgage prepayments, as well as other factors. Accordingly, estimates of fair value are as of the balance sheet dates and are not necessarily indicative of the amounts that could be realized in a current market exchange. The use of different market assumptions

and estimation methodologies may have a material effect on estimated fair values. Judgment is also exercised in making impairment conclusions and estimating impairment charges.

Amortization of investment premiums on financial assets is based in part on estimates of future levels of mortgage prepayments. Estimates are influenced by changes in, and market expectations for changes in, interest rates, market liquidity conditions, actual levels of mortgage prepayments and other factors. Judgment is required in developing these estimates, however the actual level of mortgage prepayments for a given accounting period is the single largest determinant in amortizing investment premiums.

Cash and Cash Equivalents

Cash and cash equivalents include unrestricted cash on hand and highly liquid investments with original maturities of three months or less when purchased.

Financial Assets

Capstead’s financial assets consist almost exclusively of Agency Securities classified as available-for-sale and carried at fair value with net unrealized gains and losses reported as a separate component of Accumulated other comprehensive income (loss). Loans classified as held for investment or mortgage securities classified as held-to-maturity are recorded at amortized cost (unpaid principal balance, adjusted for unamortized investment premiums and discounts). Interest is recorded as income when earned. Investment premiums and discounts are recognized as adjustments to interest income by the interest method over the expected life of the related financial assets. Realized gains and losses from any financial asset sales are recorded as a component of Other (expense) income. The specific identification method is used to determine the cost of financial assets sold. Financial assets are reviewed for potential impairment at each balance sheet date. Other-than-temporary impairments of investments in mortgage securities can occur with changes in the Company’s intent or ability to hold the mortgage securities until any declines in fair value are recovered and as a result of adverse changes in the financial condition of the issuer(s) such that a full recovery of cost basis is no longer expected. The amount of any such other-than-temporary impairment for an investment in a mortgage security is measured by comparing the recorded amount of the security to its fair value. Other-than-temporary impairment charges would be recorded as a component of Other (expense) income if the impairment results from changes in the Company’s intent or ability to hold the securities. Should other-than-temporary impairment arise as a result of adverse changes in the financial condition of the issuer(s) without changing the Company’s intent and ability to hold the securities, the credit component of the impairment would be recorded as a component of Other (expense) income with any remainder recorded as a component of Other comprehensive income (loss).

Borrowings

Secured borrowings in the form of repurchase arrangements create exposure to the potential for failure on the part of counterparties to honor their commitment to return pledged collateral. In the event of a default by a repurchase arrangement counterparty, the Company may have difficulty recovering its collateral. To mitigate this risk, the Company monitors the creditworthiness of its counterparties and manages its exposure to any single counterparty.

Capstead’s borrowings are carried at their principal balances outstanding net of related debt issuance costs and debt discounts, if applicable. Debt issuance costs associated with Unsecured borrowings are recognized as adjustments to interest expense by the interest method over the term of these borrowings.

Derivative Financial Instruments ("Derivatives")

Derivative Financial Instruments (“Derivatives”)

Derivatives used by Capstead for risk management purposes are carried at fair value as assets or liabilities. The accounting for changes in fair value of Derivatives held depends on whether it has been designated as a hedge for accounting purposes, as well as the type of hedging relationship identified. Capstead may designate any Derivatives held as cash flow hedges related to a designated portion of its current and anticipated future borrowings. To qualify as a cash flow hedge, at the inception of the hedge relationship the Company must document that the hedge relationship is anticipated to be highly effective and monitor ongoing effectiveness on at least a quarterly basis. As long as the hedge relationship remains effective, the change in fair value of the Derivatives are recorded in Accumulated other comprehensive income (loss). Changes in fair value of Derivatives not held as accounting hedges, if any, or for which the hedge relationship is no longer considered highly effective, are recorded in earnings as a component of Other (expense) income. On March 1, 2019 the Company discontinued its use of hedge accounting on its interest rate swaps related to Secured borrowings, while retaining hedge accounting for swaps related to Unsecured borrowings.

The Company uses Derivatives primarily in the form of interest rate swap agreements to hedge the variability in borrowing rates on its secured and unsecured borrowings. If designated as accounting hedges, related fixed interest payments and variable interest receipts are recorded as an adjustment to interest expense on the related designated borrowings. If not designated as accounting hedges, fixed interest payments and variable interest receipts are recorded as a component of Other (expense) income. For Derivatives initially designated as accounting hedges and subsequently de-designated, unrealized gain or loss included in Accumulated other comprehensive income (loss) at the time of de-designation is amortized as an adjustment to interest expense on the related borrowings over the remaining term of the Derivatives.

Derivatives create exposure to credit risk related to the potential for failure on the part of counterparties to honor their commitments. In addition, the Company is required to post collateral based on any declines in the market value of the Derivatives. In the event of default by a counterparty, the Company may have difficulty recovering its collateral and may not receive payments provided for under the terms of the Derivatives. To mitigate this risk, the Company uses only well-established commercial banks as counterparties and, pursuant to regulatory changes implemented in 2013, most Derivatives held at December 31, 2019 were entered into through Derivative exchanges established in part to mitigate credit risk.

Cash collateral receivable from derivative counterparties, when present, represents cash remitted to swap counterparties to meet initial and ongoing margin requirements that are based on the fair value of these Derivatives, including related interest receivable or payable under the terms of the agreements. The Company may also remit mortgage securities to certain of its swap counterparties to meet ongoing margin requirements. Such mortgage securities, if any, are included in Residential mortgage investments. Similarly, Cash collateral payable to derivative counterparties, when present, represents cash received from counterparties to meet margin call requirements. For presentation purposes, the Company does not offset individual counterparty collateral receivables (or payables) with the recorded fair value of related interest rate swap agreements pursuant to master netting arrangements. In addition, gross unrealized gains on Derivatives (recorded as assets) are stated separately from gross unrealized losses (recorded as liabilities) without regard to counterparty. Certain cash margin amounts are presented on a net basis against the fair value of related Derivatives.

Long-term Incentive Compensation

Capstead provides its employees and its directors with long-term incentive compensation in the form of equity-based awards. Equity-based compensation costs are initially measured at the estimated fair value of the awards on the grant date developed using appropriate valuation methodologies. Valuation methodologies used and subsequent expense recognition is dependent upon each award’s service and performance conditions, the latter also referred to as performance metrics. Capstead has elected not to

estimate future award forfeitures when valuing equity-based awards and will adjust compensation costs as actual forfeitures occur.

Compensation costs for equity-based awards subject only to service conditions are measured at the closing stock price on the dates of grant and are recognized as expense on a straight-line basis over the requisite service periods for the awards, as adjusted for any forfeitures. Compensation costs for components of equity-based awards subject to nonmarket-based performance metrics (i.e. metrics not predicated on changes in the Company’s stock price), are measured at the closing stock price on the dates of grant, adjusted for the probability of achieving benchmarks included in the performance metrics. These initial cost estimates are recognized as expense over the requisite performance periods, adjusted for subsequent changes in performance estimates. Compensation costs for components of equity-based awards subject to market-based performance metrics are measured at the dates of grant using Monte Carlo simulations which incorporate into the valuations the inherent uncertainty regarding achieving the market-based performance metrics. These initial valuation amounts are recognized as expense over the requisite performance periods, subject to adjustments only for actual forfeitures.

Income Taxes

Capstead Mortgage Corporation and its qualified REIT subsidiaries (“Capstead REIT”) have elected to be taxed as a REIT. As a result, Capstead REIT is not taxed on taxable income distributed to stockholders if certain REIT qualification tests are met. Capstead’s policy is to distribute 100% of its taxable income, after application of available tax attributes, within the time limits prescribed by the Internal Revenue Code (the “Code”), which may extend into the subsequent taxable year. The Company may find it advantageous from time to time to elect taxable REIT subsidiary status for certain of its subsidiaries in which case taxable income of any such subsidiary would be subject to federal and, where applicable, state or local income taxes. Any such income taxes are accounted for using the liability method. Related deferred income tax assets and liabilities are determined based on differences between the financial reporting and tax bases of assets and liabilities and are measured using enacted tax rates and laws that will be in effect when the differences are expected to reverse. The Company has not recognized any liabilities for unrecognized tax benefits using a “more likely than not” threshold for the recognition and measurement of the financial statement effects of tax positions taken on a tax return filing. Should any such liabilities be recognized in future periods, the Company will record related interest and penalties in Other general and administrative expense.

Dividend Classification

The tax and financial reporting classification of dividends can differ primarily as a result of differences between taxable income attributable to a particular tax year and that year’s Net income (loss), the amount and timing of dividends paid relative to taxable income and how such taxable income is allocated to dividends paid.