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		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	$ 59	$ 50	$ 56	$ 54
Charge-offs	(2)	(3)	(6)	(8)
Recoveries	1		2	1
Provision for loan losses	(1)	4	5	4
Balance at end of period	57	51	57	51
Residential real estate mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	40	37	36	40
Charge-offs	(1)	(1)	(3)	(4)
Recoveries			1	1
Provision for loan losses	1	(2)	6	(3)
Balance at end of period	40	34	40	34
Home equity lines of credit [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	19	13	20	14
Charge-offs	(1)	(2)	(3)	(4)
Recoveries	1		1
Provision for loan losses	(2)	6	(1)	7
Balance at end of period	$ 17	$ 17	$ 17	$ 17