Business	6 Months Ended
Jun. 30, 2011
Business
Business	NOTE 1 — BUSINESS Capstead Mortgage Corporation operates as a self-managed real estate investment trust for federal income tax purposes (a "REIT") and is based in Dallas, Texas. Unless the context otherwise indicates, Capstead Mortgage Corporation, together with its subsidiaries, is referred to as "Capstead" or the "Company." Capstead earns income from investing in a leveraged portfolio of residential mortgage pass-through securities consisting almost exclusively of adjustable-rate mortgage ("ARM") securities issued and guaranteed by government-sponsored enterprises, either Fannie Mae or Freddie Mac (together, the "GSEs"), or by an agency of the federal government, Ginnie Mae. Agency-guaranteed residential mortgage pass-through securities ("Agency Securities") are considered to have limited, if any, credit risk, particularly in light of the conservatorship of the GSEs by the federal government.

The entire disclosure for the nature of an entity's business, the major products or services it sells or provides and its principal markets, including the locations of those markets. If the entity operates in more than one business, the disclosure also indicates the relative importance of its operations in each business and the basis for the determination (for example, assets, revenues, or earnings).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Name Statement of Position (SOP)
-Publisher AICPA
-Number 94-6
-Paragraph 10
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6003-108592

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