Unpaid losses and loss expenses (A&E Loss Roll-forward) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2013
Unpaid Losses and Loss Expenses [Roll Forward]
Balance (gross) at December 31, 2012	$ 2,080
Balance (net) at December 31, 2012	1,106
Incurred activity, gross	244
Incurred activity, net	171
Paid activity, gross	(485)
Paid activity, net	(226)
Balance (gross) at December 31, 2013	1,839
Balance (net) at December 31, 2013	1,051
Asbestos
Unpaid Losses and Loss Expenses [Roll Forward]
Balance (gross) at December 31, 2012	1,886
Balance (net) at December 31, 2012	970
Incurred activity, gross	125
Incurred activity, net	96
Paid activity, gross	(367)
Paid activity, net	(140)
Balance (gross) at December 31, 2013	1,644
Balance (net) at December 31, 2013	926
Environmental
Unpaid Losses and Loss Expenses [Roll Forward]
Balance (gross) at December 31, 2012	194
Balance (net) at December 31, 2012	136
Incurred activity, gross	119
Incurred activity, net	75
Paid activity, gross	(118)
Paid activity, net	(86)
Balance (gross) at December 31, 2013	195
Balance (net) at December 31, 2013	$ 125

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Carrying amount as of the balance sheet date of reserves for the costs of settling insured claims and costs incurred in the claims settlement process attributable to asbestos and environmental claims, before estimated recoveries from reinsurers.

+ References

+ Details

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- Definition

Amount of asbestos claims paid in the current period, before estimated recoveries from reinsurers.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 40

-Section 50

-Paragraph 3

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6482485&loc=d3e14764-158437

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 40

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6482485&loc=d3e14784-158437

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- Definition

Increase in asbestos and environmental reserve based on known and estimated costs of settling insured claims and costs incurred in the claims settlement process, before estimated recoveries from reinsurers.

+ References

+ Details

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- Definition

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- Definition

Amount of asbestos claims paid in the current period, net of reinsurance recoveries.

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Increase in asbestos and environmental reserve based on known and estimated costs of settling insured claims and costs incurred in the claims settlement process, net of estimated reinsurance recoveries.

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