Bank Loans and Related Allowance for Credit Losses (Changes in Allowance for Credit Losses) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	$ 18	$ 29	$ 30	$ 18
Recoveries	0	1	0	1
Provision for loan losses	(5)	0	(17)	10
Balance at end of period	13	30	13	30
Adoption of ASU 2016-13 [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period			0	1
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	15	25	27	15
Recoveries	0	1	0	1
Provision for loan losses	(5)	0	(17)	9
Balance at end of period	10	26	10	26
Residential Real Estate [Member] | Adoption of ASU 2016-13 [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period			0	1
First Mortgage [Member] | Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	12	21	22	11
Recoveries	0	1	0	1
Provision for loan losses	(4)	0	(14)	9
Balance at end of period	8	22	8	22
First Mortgage [Member] | Residential Real Estate [Member] | Adoption of ASU 2016-13 [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period			0	1
HELOCs [Member] | Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	3	4	5	4
Recoveries	0	0	0	0
Provision for loan losses	(1)	0	(3)	0
Balance at end of period	2	4	2	4
HELOCs [Member] | Residential Real Estate [Member] | Adoption of ASU 2016-13 [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period			0	0
Other [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period	3	4	3	3
Recoveries	0	0	0	0
Provision for loan losses	0	0	0	1
Balance at end of period	$ 3	$ 4	3	4
Other [Member] | Adoption of ASU 2016-13 [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of period			$ 0	$ 0