Including the current and noncurrent portions, carrying value as of the balance sheet date of uncollateralized debt obligations (with maturities initially due after one year or beyond the operating cycle if longer).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 5
-Section 02
-Subsection 19, 20, 22

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 16
-Article 9

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.16)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.16)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Name:	us-gaap_UnsecuredDebt
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Unsecured Borrowings (Schedule Of Subordinated Note Balances And Related Weighted Average Interest Rate) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010
Junior subordinated notes, borrowings outstanding	$ 103,095	$ 103,095
Junior subordinated notes, average rate	8.49%		8.49%
Capstead Mortgage Trust I [Member]
Junior subordinated notes, borrowings outstanding	36,083
Junior subordinated notes, average rate	8.31%
Capstead Mortgage Trust II [Member]
Junior subordinated notes, borrowings outstanding	41,238
Junior subordinated notes, average rate	8.46%
Capstead Mortgage Trust III [Member]
Junior subordinated notes, borrowings outstanding	$ 25,774
Junior subordinated notes, average rate	8.78%