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		9 Months Ended		3 Months Ended	9 Months Ended			3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2013 Residential real estate mortgages [Member]	Sep. 30, 2014 Residential real estate mortgages [Member]	Sep. 30, 2013 Residential real estate mortgages [Member]	Jun. 30, 2014 Residential real estate mortgages [Member]	Sep. 30, 2014 Home equity lines of credit [Member]	Sep. 30, 2013 Home equity lines of credit [Member]	Sep. 30, 2014 Home equity lines of credit [Member]	Sep. 30, 2013 Home equity lines of credit [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	$ 41	$ 57	$ 48	$ 56	$ 40	$ 34	$ 36	$ 28	$ 13	$ 17	$ 14	$ 20
Charge-offs		(2)	(3)	(8)	(1)	(1)	(4)			(1)	(2)	(4)
Recoveries		1	2	3	1	1	2				1	1
Provision for loan losses	(1)	(4)	(7)	1	(6)	(6)			(1)	2	(1)	1
Balance at end of period	$ 40	$ 52	$ 40	$ 52	$ 34	$ 28	$ 34	$ 28	$ 12	$ 18	$ 12	$ 18