UNSECURED BORROWINGS - Narrative (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013
Debt Instrument [Line Items]
Junior subordinated notes maturity term	30 years
Issuance of common securities	$ 3.1
Remaining issue costs	2.2
Capstead Mortgage Trust I [Member]
Debt Instrument [Line Items]
Junior subordinated notes, maturity period	Oct. 31, 2035
Capstead Mortgage Trust II [Member]
Debt Instrument [Line Items]
Junior subordinated notes, maturity period	Dec. 31, 2035
Junior subordinated notes, earliest redemption option exercise date	Dec. 15, 2015
Capstead Mortgage Trust III [Member]
Debt Instrument [Line Items]
Junior subordinated notes, maturity period	Sep. 30, 2036
Junior subordinated notes, earliest redemption option exercise date	Sep. 15, 2016
Interest paid on outstanding borrowings	8.6
Special-Purpose Statutory Trusts [Member]
Debt Instrument [Line Items]
Issuance of common securities	3.1
Proceeds from private placement of preferred securities	$ 100