Total Equity (AOCI) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Cumulative adjustment for accounting changes	$ (131)	$ 10
Accumulated Other Comprehensive Income (Loss)
Beginning balance	(3,060)	(2,643)
Cumulative adjustment for accounting changes	(437)
OCI during the period	91	193
Ending balance	(3,406)	(2,450)
Foreign Currency Translation Adjustments
Beginning balance	(767)	(986)
Cumulative adjustment for accounting changes	(8)
OCI during the period	60	107
Ending balance	(715)	(879)
AFS Securities
Beginning balance	(547)	(588)
Cumulative adjustment for accounting changes	(111)
OCI during the period	(410)	84
Ending balance	(1,068)	(504)
Pension, Postretirement and Other
Beginning balance	(591)	(474)
Cumulative adjustment for accounting changes	(124)
OCI during the period	5	0
Ending balance	(710)	(474)
DVA
Beginning balance	(1,155)	(595)
Cumulative adjustment for accounting changes	(194)
OCI during the period	436	2
Ending balance	$ (913)	$ (593)

Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e637-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e681-108580

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669686-108580

Name:	us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant