Regulatory Capital and Other Regulatory Matters - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Capital Requirements on Foreign Financial Institutions [Line Items]
Assets	$ 97,015	$ 87,765
Brazil [Member]
Capital Requirements on Foreign Financial Institutions [Line Items]
Capital ratio	17.40%
Capital requirement	10.50%
International Regulated Bank And Finance Companies [Member]
Capital Requirements on Foreign Financial Institutions [Line Items]
Assets	$ 7,800	$ 6,900

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(12))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(11))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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- Definition

The minimum Total risk based capital ratio (total capital divided by risk weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958568-112826

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1H
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=84167132&loc=d3e65071-112826

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=84167132&loc=SL5958570-112826

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Total Capital divided by risk weighted assets as defined in the regulations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1H
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=84167132&loc=d3e65071-112826

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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