Loans to Banking Clients and Related Allowance for Loan Losses (Changes in Allowance for Loan Losses) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of year	$ 48	$ 56
Charge-offs	(2)	(4)
Recoveries	1	1
Provision for loan losses	1	6
Balance at end of year	48	59
Residential real estate mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of year	34	36
Charge-offs	(1)	(2)
Recoveries		1
Provision for loan losses		5
Balance at end of year	33	40
Home equity lines of credit [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of year	14	20
Charge-offs	(1)	(2)
Recoveries	1
Provision for loan losses	1	1
Balance at end of year	$ 15	$ 19