Bank Loans and Related Allowance for Loan Losses (Changes in Allowance for Loan Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	$ 26	$ 31	$ 42
Charge-offs	(3)	(2)	(3)
Recoveries	3	2	3
Provision for loan losses	0	(5)	(11)
Balance at end of year	26	26	31
First Mortgage [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	17	20	29
Charge-offs	(2)	(1)	(1)
Recoveries	1	1	1
Provision for loan losses	0	(3)	(9)
Balance at end of year	16	17	20
HELOC's [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	8	11	13
Charge-offs	(1)	(1)	(2)
Recoveries	1	1	2
Provision for loan losses	0	(3)	(2)
Balance at end of year	8	8	11
Other [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	1	0
Charge-offs	0	0
Recoveries	1	0
Provision for loan losses	0	1
Balance at end of year	$ 2	$ 1	$ 0