Bank Loans and Related Allowance for Loan Losses (Changes in Allowance for Loan Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	$ 42	$ 48	$ 56
Charge-offs	(3)	(5)	(11)
Recoveries	3	3	4
Provision for loan losses	(11)	(4)	(1)
Balance at end of period	31	42	48
Residential real estate mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	29	34	36
Charge-offs	(1)	(3)	(5)
Recoveries	1	2	2
Provision for loan losses	(9)	(4)	1
Balance at end of period	20	29	34
Home equity loans and lines of credit [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	13	14	20
Charge-offs	(2)	(2)	(6)
Recoveries	2	1	2
Provision for loan losses	(2)		(2)
Balance at end of period	$ 11	$ 13	$ 14