Bank Loans and Related Allowance for Loan Losses (Credit Quality Indicators of Bank Loan Portfolio) (Details) $ in Millions	Jun. 30, 2017 USD ($) credit_rating	Dec. 31, 2016 USD ($) credit_rating
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 15,843	$ 15,429
Residential real estate mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 9,581	$ 9,134
Weighted Average Updated FICO | credit_rating	774	773
Percent of Loans on Nonaccrual Status	0.09%	0.10%
Residential real estate mortgages [Member] | Origination FICO Score Below 620 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 7	$ 8
Residential real estate mortgages [Member] | Origination FICO Score 620 Through 679 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	85	92
Residential real estate mortgages [Member] | Origination FICO Score 680 Through 739 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	1,491	1,427
Residential real estate mortgages [Member] | Origination FICO Score 740 And Above [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	7,998	7,607
Residential real estate mortgages [Member] | Year of origination Pre 2013 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	1,808	2,136
Residential real estate mortgages [Member] | Year of origination 2013 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	1,534	1,746
Residential real estate mortgages [Member] | Year of origination 2014 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	599	685
Residential real estate mortgages [Member] | Year of origination 2015 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	1,351	1,458
Residential real estate mortgages [Member] | Year of origination 2016 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	3,037	3,109
Residential real estate mortgages [Member] | Year of origination 2017 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	1,252
Residential real estate mortgages [Member] | Estimated Current LTV 70% And Below [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 8,648	$ 8,350
Weighted Average Updated FICO | credit_rating	775	774
Percent of Loans on Nonaccrual Status	0.03%	0.04%
Residential real estate mortgages [Member] | Estimated Current LTV Greater Than 70% through 90% [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 898	$ 743
Weighted Average Updated FICO | credit_rating	768	768
Percent of Loans on Nonaccrual Status	0.30%	0.35%
Residential real estate mortgages [Member] | Estimated Current LTV Greater Than 90% through 100% [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 16	$ 21
Weighted Average Updated FICO | credit_rating	740	747
Percent of Loans on Nonaccrual Status	2.93%	2.08%
Residential real estate mortgages [Member] | Estimated Current LTV Greater Than 100% [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 19	$ 20
Weighted Average Updated FICO | credit_rating	698	709
Percent of Loans on Nonaccrual Status	17.07%	14.50%
Residential real estate mortgages [Member] | Origination Loan To Value Ratio 70% And Below [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 7,237	$ 6,865
Residential real estate mortgages [Member] | Origination Loan to Value Ratio Greater Than 70% Through 90% [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	2,336	2,260
Residential real estate mortgages [Member] | Origination Loan to Value Ratio Greater Than 90% Through 100% [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	8	9
Home equity loans and lines of credit [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 2,148	$ 2,350
Weighted Average Updated FICO | credit_rating	770	769
Utilization Rate	35.00%	36.00%
Percent of Loans on Nonaccrual Status	0.19%	0.20%
Home equity loans and lines of credit [Member] | Origination FICO Score Below 620 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 0	$ 0
Home equity loans and lines of credit [Member] | Origination FICO Score 620 Through 679 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	11	13
Home equity loans and lines of credit [Member] | Origination FICO Score 680 Through 739 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	396	432
Home equity loans and lines of credit [Member] | Origination FICO Score 740 And Above [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	1,741	1,905
Home equity loans and lines of credit [Member] | Year of origination Pre 2013 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	1,553	1,765
Home equity loans and lines of credit [Member] | Year of origination 2013 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	169	193
Home equity loans and lines of credit [Member] | Year of origination 2014 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	137	152
Home equity loans and lines of credit [Member] | Year of origination 2015 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	140	146
Home equity loans and lines of credit [Member] | Year of origination 2016 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	104	94
Home equity loans and lines of credit [Member] | Year of origination 2017 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	45
Home equity loans and lines of credit [Member] | Estimated Current LTV 70% And Below [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 1,893	$ 2,070
Weighted Average Updated FICO | credit_rating	772	771
Utilization Rate	33.00%	35.00%
Percent of Loans on Nonaccrual Status	0.10%	0.12%
Home equity loans and lines of credit [Member] | Estimated Current LTV Greater Than 70% through 90% [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 216	$ 234
Weighted Average Updated FICO | credit_rating	759	757
Utilization Rate	49.00%	50.00%
Percent of Loans on Nonaccrual Status	0.19%	0.40%
Home equity loans and lines of credit [Member] | Estimated Current LTV Greater Than 90% through 100% [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 23	$ 29
Weighted Average Updated FICO | credit_rating	743	747
Utilization Rate	65.00%	66.00%
Percent of Loans on Nonaccrual Status	0.98%	1.74%
Home equity loans and lines of credit [Member] | Estimated Current LTV Greater Than 100% [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 16	$ 17
Weighted Average Updated FICO | credit_rating	730	728
Utilization Rate	73.00%	70.00%
Percent of Loans on Nonaccrual Status	8.87%	3.73%
Home equity loans and lines of credit [Member] | Origination Loan To Value Ratio 70% And Below [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 1,491	$ 1,628
Home equity loans and lines of credit [Member] | Origination Loan to Value Ratio Greater Than 70% Through 90% [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	646	709
Home equity loans and lines of credit [Member] | Origination Loan to Value Ratio Greater Than 90% Through 100% [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	11	13
Pledged asset lines [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	4,001	3,851
Pledged asset lines [Member] | Weighted Average Loan to Value Ratio =70% [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 4,001	$ 3,851
Weighted Average Updated FICO | credit_rating	767	763
Utilization Rate	43.00%	46.00%
Percent of Loans on Nonaccrual Status	0.00%	0.00%