Retained Earnings and Regulatory Capital Requirements Retained Earnings and Regulatory Capital Requirements - Additional Information (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
Jun. 30, 2013	Dec. 31, 2012
Banking and Thrift [Abstract]
Contributions	$ 0
Distributions	0
Deferred tax assets excluded in computation of regulatory capital	$ 557	$ 622

The cash inflow from parent as a source of financing that is recorded as additional paid in capital.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 14

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration