Securities financing activities - Schedule of transfers not qualifying for sale accounting (Details) - USD ($) $ in Billions	Sep. 30, 2015	Dec. 31, 2014
Securities Financing Transactions Disclosures [Abstract]
Transfers not qualifying for sale accounting	$ 11.2	$ 13.8

Carrying amount of financial assets accounted for as secured borrowings recognized in the transferor's statement of financial position at the end of each period presented.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 30

-Section 50

-Paragraph 1A

-Subparagraph (b)(1)

-URI http://asc.fasb.org/extlink&oid=55761124&loc=SL6224234-111729

Name:	us-gaap_TransfersAccountedForAsSecuredBorrowingsAssetsCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant