Debt and Credit Arrangements - Long Term Debt (Parenthetical) (Detail)	12 Months Ended
Dec. 31, 2014
Debt Instrument [Line Items]
Interest rate of capital securities march 29, 2067	6.375%cb_InterestRateOfCapitalSecurities
5.75% Notes due May 15, 2018 [Member]
Debt Instrument [Line Items]
Interest rate due on notes and debentures	5.75%
Debt instrument maturity date	May 15, 2018
6.6% Debentures due August 15, 2018 [Member]
Debt Instrument [Line Items]
Interest rate due on notes and debentures	6.60%
Debt instrument maturity date	Aug. 15, 2018
6.8% Debentures due November 15, 2031 [Member]
Debt Instrument [Line Items]
Interest rate due on notes and debentures	6.80%
Debt instrument maturity date	Nov. 15, 2031
6% Notes due May 11, 2037 [Member]
Debt Instrument [Line Items]
Interest rate due on notes and debentures	6.00%
Debt instrument maturity date	May 11, 2037
6.5% Notes due May 15, 2038 [Member]
Debt Instrument [Line Items]
Interest rate due on notes and debentures	6.50%
Debt instrument maturity date	May 15, 2038
6.375% Capital Securities due March 29, 2067 [Member]
Debt Instrument [Line Items]
Interest rate of capital securities march 29, 2067	6.375%
Debt instrument maturity date	Mar. 29, 2067

Interest rate for the contractual debt agreement through a certain date.

No definition available.

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Period Type:	duration

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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- Details

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Period Type:	duration

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(2))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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- Details

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