Bank Loans and Related Allowance for Credit Losses (Changes in Allowance for Credit Losses) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 18	$ 21
Charge-offs	0	0
Recoveries	0	1
Provision for loan losses	10	(1)
Balance at end of period	29	21
First Mortgage [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	11	14
Charge-offs	0	0
Recoveries	0	0
Provision for loan losses	9	0
Balance at end of period	21	14
HELOCs [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	4	5
Charge-offs	0	0
Recoveries	0	1
Provision for loan losses	0	(1)
Balance at end of period	4	5
Other [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	3	2
Charge-offs	0	0
Recoveries	0	0
Provision for loan losses	1	0
Balance at end of period	4	2
Adoption of ASU 2016-13 [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	1	0
Adoption of ASU 2016-13 [Member] | First Mortgage [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	1	0
Adoption of ASU 2016-13 [Member] | HELOCs [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	0	0
Adoption of ASU 2016-13 [Member] | Other [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 0	$ 0