Unpaid losses and loss expenses (Brandywine Incurred Loss Activity) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Unpaid Losses and Loss Expenses [Roll Forward]
Balance at beginning of year	$ 27,008	$ 26,831	$ 26,547
Incurred activity	9,484	9,649	9,348
Paid activity	9,665	9,235	8,977
Balance at end of year	$ 26,562	$ 27,008	$ 26,831

Unpaid Losses and Loss Expenses [Roll Forward]

No definition available.

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- Definition

Amount of expense for claims incurred and costs incurred in the claim settlement process.

+ References

+ Details

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- Definition

Liability as of the balance sheet date for amounts representing estimated cost of settling unpaid claims under the terms of the underlying insurance policies, less estimated reinsurance recoveries on such claims. This includes an estimate for claims which have been incurred but not reported. Claim adjustment expenses represent the costs estimated to be incurred in the settlement of unpaid claims.

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

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 13
-Subparagraph a
-Article 7

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Financial Reporting Release (FRR)
-Number 403
-Paragraph 04
-Subparagraph b

+ Details

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- Definition

Amount of payments to settle insured claims and pay costs incurred in the claims settlement process.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3536-108585

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