Business Acquisition - Additional Information (Detail) (optionsXpress Holdings, Inc., USD $) In Millions, except Per Share data	1 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Sep. 01, 2011
optionsXpress Holdings, Inc.
Business Acquisition [Line Items]
Business acquisition, consideration paid						$ 714
Common shares issued per each share of acquiree						$ 1.02
Business acquisition, common stock issued share						59
Fair value of common stock issued						710
Fair value of stock-based compensation awards assumed from the acquisition						4
Preliminary goodwill						507	[1]
Business acquisition, preliminary intangible assets						285
Net revenue, acquiree	17
Net loss, acquiree	(2)
Acquisition related costs, after tax, incurred by the Company and excluded from proforma net income		10
Acquisition related costs, after tax, incurred by the Company and included in proforma net income for the prior period and excluded from proforma net income in the current period				12	12
Acquisition related costs, before tax, incurred by optionsXpress Holdings, Inc., prior to the acquisition date and excluded from proforma net income		15	15	15	15
Amortization of purchase accounting adjustments related to intangible assets of optionsXpress Holdings, Inc., net of tax		$ 6	$ 6	$ 17	$ 18

[1] Represents a non-cash investing activity.