BUSINESS	12 Months Ended
Dec. 31, 2015
BUSINESS [Abstract]
BUSINESS	NOTE 1 ¾ 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, Freddie Mac, or by an agency of the federal government, Ginnie Mae. Residential mortgage pass-through securities guaranteed by Fannie Mae, Freddie Mac or Ginnie Mae are referred to as “Agency Securities” and are considered to have limited, if any, credit risk.

BUSINESS

12 Months Ended

Dec. 31, 2015

NOTE 1 ¾ 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, Freddie Mac, or by an agency of the federal government, Ginnie Mae. Residential mortgage pass-through securities guaranteed by Fannie Mae, Freddie Mac or Ginnie Mae are referred to as “Agency Securities” and are considered to have limited, if any, credit risk.