Bank Loans and Related Allowance for Loan Losses (Changes in Allowance for Loan Losses) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	$ 19	$ 26	$ 21	$ 26
Charge-offs	0	0	0	(1)
Recoveries	0	1	2	2
Provision for loan losses	(2)	(1)	(6)	(1)
Balance at end of period	17	26	17	26
First Mortgage [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	12	17	14	16
Charge-offs	0	0	0	0
Recoveries	0	0	1	0
Provision for loan losses	(2)	0	(5)	1
Balance at end of period	10	17	10	17
HELOCs [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	5	7	5	8
Charge-offs	0	0	0	0
Recoveries	0	1	1	2
Provision for loan losses	(1)	(1)	(2)	(3)
Balance at end of period	4	7	4	7
Other [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	2	2	2	2
Charge-offs	0	0	0	(1)
Recoveries	0	0	0	0
Provision for loan losses	1	0	1	1
Balance at end of period	$ 3	$ 2	$ 3	$ 2