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 Year
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
Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	70
Estimated Useful Life (In Years)	9
Trade Name
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value	$ 15
Estimated Useful Life (In Years)	9

The calculated weighted-average amortization period of a major class of finite-lived intangible assets acquired during the current period either individually or as part of a group of assets (in either an asset acquisition or business combination). A major class is composed of intangible assets that can be grouped together because they are similar, either by their nature or by their use in the operations of a company.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 142

-Paragraph 44

-Subparagraph a(3)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (a)(3)

-URI http://asc.fasb.org/extlink&oid=6905858&loc=d3e16265-109275

Name:	us-gaap_AcquiredFiniteLivedIntangibleAssetWeightedAverageUsefulLife
Namespace Prefix:	us-gaap
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration