Bank Loans and Related Allowance for Loan Losses (Changes in Allowance for Loan Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	$ 31	$ 42	$ 48
Charge-offs	(2)	(3)	(5)
Recoveries	2	3	3
Provision for loan losses	(5)	(11)	(4)
Balance at end of period	26	31	42
Residential real estate mortgages [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	20	29	34
Charge-offs	(1)	(1)	(3)
Recoveries	1	1	2
Provision for loan losses	(3)	(9)	(4)
Balance at end of period	17	20	29
Home equity loans and lines of credit [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period	11	13	14
Charge-offs	(1)	(2)	(2)
Recoveries	1	2	1
Provision for loan losses	(3)	(2)
Balance at end of period	8	11	$ 13
Other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period
Charge-offs
Recoveries
Provision for loan losses	1
Balance at end of period	$ 1