Name:	cmo_AmortizedCostBasis
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The carrying amount as of the balance sheet date of firm holdings in mortgages, mortgage backed securities (investment instruments that represent ownership of an undivided interest in a group of mortgages, where principal and interest from the individual mortgages are used to pay investors' principal and interest on the mortgage backed security) senior debt securities, residential mortgage loans, and asset-backed securities that are primarily paid from the cash flows of a discrete pool of receivables or other financial assets (such as credit-card receivables), either fixed or revolving, that by their terms convert into cash within a finite time period. Includes both pledged (to counterparties as collateral for financing transactions) and unpledged holdings.

No definition available.

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The calculated weighted average effective interest rate of the securities presented for the period then ended, calculated including the amortization of investment premiums and excluding unrealized gains and losses.

No definition available.

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Namespace Prefix:	cmo_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Amount of premium originally recognized at the purchase of the security that is yet to be amortized.

No definition available.

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Net WAC is presented net of servicing and other fees and represents the cash yield inherent in the portfolio as of the indicated balance sheet date, before amortization of investment premiums.

No definition available.

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Data Type:	num:percentItemType
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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Data Type:	xbrli:stringItemType
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For investments which are quantified by principal amount, the principle balance held at close of period.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 210
-Section 50
-Paragraph 6
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=99383244&loc=d3e12121-115841

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 320
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-12B(Column B))
-URI http://asc.fasb.org/extlink&oid=120401592&loc=d3e611197-123010

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Data Type:	xbrli:monetaryItemType
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