Bank Loans and Related Allowance for Loan Losses (Credit Quality Indicators of Bank Loan Portfolio) (Details) $ in Millions	Mar. 31, 2017 USD ($) credit_rating	Dec. 31, 2016 USD ($) credit_rating
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 15,574	$ 15,429
Residential real estate mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 9,398	$ 9,134
Weighted Average Updated FICO | credit_rating	776	773
Percent of Loans on Nonaccrual Status	0.10%	0.10%
Residential real estate mortgages [Member] | Origination FICO Score Below 620 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 8	$ 8
Residential real estate mortgages [Member] | Origination FICO Score 620 Through 679 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	90	92
Residential real estate mortgages [Member] | Origination FICO Score 680 Through 739 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	1,462	1,427
Residential real estate mortgages [Member] | Origination FICO Score 740 And Above [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	7,838	7,607
Residential real estate mortgages [Member] | Year of origination Pre 2013 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	1,991	2,136
Residential real estate mortgages [Member] | Year of origination 2013 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	1,642	1,746
Residential real estate mortgages [Member] | Year of origination 2014 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	642	685
Residential real estate mortgages [Member] | Year of origination 2015 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	1,413	1,458
Residential real estate mortgages [Member] | Year of origination 2016 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	3,113	3,109
Residential real estate mortgages [Member] | Year of origination 2017 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	597
Residential real estate mortgages [Member] | Estimated Current LTV 70% And Below [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 8,496	$ 8,350
Weighted Average Updated FICO | credit_rating	776	774
Percent of Loans on Nonaccrual Status	0.02%	0.04%
Residential real estate mortgages [Member] | Estimated Current LTV Greater Than 70% through 90% [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 863	$ 743
Weighted Average Updated FICO | credit_rating	770	768
Percent of Loans on Nonaccrual Status	0.31%	0.35%
Residential real estate mortgages [Member] | Estimated Current LTV Greater Than 90% through 100% [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 19	$ 21
Weighted Average Updated FICO | credit_rating	774	747
Percent of Loans on Nonaccrual Status	5.24%	2.08%
Residential real estate mortgages [Member] | Estimated Current LTV Greater Than 100% [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 20	$ 20
Weighted Average Updated FICO | credit_rating	693	709
Percent of Loans on Nonaccrual Status	18.80%	14.50%
Residential real estate mortgages [Member] | Origination Loan To Value Ratio 70% And Below [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 7,098	$ 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	2,292	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	$ 2,230	$ 2,350
Weighted Average Updated FICO | credit_rating	771	769
Utilization Rate	35.00%	36.00%
Percent of Loans on Nonaccrual Status	0.24%	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	12	13
Home equity loans and lines of credit [Member] | Origination FICO Score 680 Through 739 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	410	432
Home equity loans and lines of credit [Member] | Origination FICO Score 740 And Above [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	1,808	1,905
Home equity loans and lines of credit [Member] | Year of origination Pre 2013 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	1,649	1,765
Home equity loans and lines of credit [Member] | Year of origination 2013 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	179	193
Home equity loans and lines of credit [Member] | Year of origination 2014 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	146	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	98	94
Home equity loans and lines of credit [Member] | Year of origination 2017 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	18
Home equity loans and lines of credit [Member] | Estimated Current LTV 70% And Below [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 1,956	$ 2,070
Weighted Average Updated FICO | credit_rating	773	771
Utilization Rate	34.00%	35.00%
Percent of Loans on Nonaccrual Status	0.15%	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	$ 230	$ 234
Weighted Average Updated FICO | credit_rating	759	757
Utilization Rate	49.00%	50.00%
Percent of Loans on Nonaccrual Status	0.34%	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	$ 26	$ 29
Weighted Average Updated FICO | credit_rating	748	747
Utilization Rate	67.00%	66.00%
Percent of Loans on Nonaccrual Status	1.30%	1.74%
Home equity loans and lines of credit [Member] | Estimated Current LTV Greater Than 100% [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 18	$ 17
Weighted Average Updated FICO | credit_rating	732	728
Utilization Rate	72.00%	70.00%
Percent of Loans on Nonaccrual Status	7.86%	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	$ 1,542	$ 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	675	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	13	13
Pledged asset lines [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	3,845	3,851
Pledged asset lines [Member] | Weighted Average Loan to Value Ratio =70% [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 3,845	$ 3,851
Weighted Average Updated FICO | credit_rating	771	763
Utilization Rate	44.00%	46.00%
Percent of Loans on Nonaccrual Status	0.00%	0.00%