Summary of Estimated Fair Value and Useful Lives of Intangible Assets (Detail) (OptionsXpress Holdings, Inc., USD $) In Millions, unless otherwise specified	1 Months Ended
Sep. 01, 2011
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	$ 285
Customer Relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	200
Estimated Useful Life (In Years)	11 years
Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	70
Estimated Useful Life (In Years)	9 years
Trade Name
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	$ 15
Estimated Useful Life (In Years)	9 years

The amount of acquisition cost of a business combination allocated to an identifiable intangible asset that will be amortized.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 51

-Subparagraph e

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 52

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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