UNSECURED BORROWINGS - Schedule of Subordinated Note Balances and Related Weighted Average Interest Rate (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013
Debt Instrument [Line Items]
Borrowings Outstanding	100,000		$ 100,000
For Final 20 Years [Member]
Debt Instrument [Line Items]
Effective borrowing rate considering cash flow hedges	7.56%
Capstead Mortgage Trust I [Member]
Debt Instrument [Line Items]
Borrowings Outstanding	35,000		35,000
Average Rate (in hundredths)	8.31%	[1]	8.31%	[1]
Capstead Mortgage Trust II [Member]
Debt Instrument [Line Items]
Borrowings Outstanding	40,000		40,000
Average Rate (in hundredths)	8.46%	[1]	8.46%	[1]
Capstead Mortgage Trust III [Member]
Debt Instrument [Line Items]
Borrowings Outstanding	25,000		25,000
Average Rate (in hundredths)	8.78%	[1]	8.78%	[1]
Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Borrowings Outstanding	100,000		$ 100,000
Average Rate (in hundredths)	8.49%	[1]	8.49%	[1]

[1] The indicated weighted average rates have been in effect since issuance. After considering cash flow hedges that coincide with the floating rate terms of these borrowings that begin October 30, and December 15, 2015 for the notes associated with Capstead Mortgage Trusts I and II and September 15, 2016 for the notes associated with Capstead Mortgage Trust III, the effective borrowing rate will average 7.56% beginning September 15, 2016 through maturity, subject to certain adjustments for the effects of measured hedge ineffectiveness, if any.