Bank Loans and Related Allowance for Loan Losses (Credit Quality Indicators of Bank Loan Portfolio) (Details) $ in Millions	Dec. 31, 2016 USD ($) item	Dec. 31, 2015 USD ($) item
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 15,429	$ 14,365
Residential real estate mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 9,134	$ 8,334
Weighted Average Updated FICO | item	773	773
Percent of Loans on Nonaccrual Status	0.10%	0.11%
Residential real estate mortgages [Member] | Origination FICO Score Below 620 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 8	$ 10
Residential real estate mortgages [Member] | Origination FICO Score 620 Through 679 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	92	88
Residential real estate mortgages [Member] | Origination FICO Score 680 Through 739 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	1,427	1,381
Residential real estate mortgages [Member] | Origination FICO Score 740 And Above [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	7,607	6,855
Residential real estate mortgages [Member] | Year of origination Pre 2012 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	1,010	1,306
Residential real estate mortgages [Member] | Year of origination 2012 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	1,126	1,644
Residential real estate mortgages [Member] | Year of origination 2013 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	1,746	2,450
Residential real estate mortgages [Member] | Year of origination 2014 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	685	1,021
Residential real estate mortgages [Member] | Year of origination 2015 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	1,458	1,913
Residential real estate mortgages [Member] | Year of origination 2016 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	3,109
Residential real estate mortgages [Member] | Estimated Current LTV 70% And Below [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 8,350	$ 7,508
Weighted Average Updated FICO | item	774	774
Percent of Loans on Nonaccrual Status	0.04%	0.03%
Residential real estate mortgages [Member] | Estimated Current LTV Greater Than 70% through 90% [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 743	$ 759
Weighted Average Updated FICO | item	768	764
Percent of Loans on Nonaccrual Status	0.35%	0.31%
Residential real estate mortgages [Member] | Estimated Current LTV Greater Than 90% through 100% [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 21	$ 37
Weighted Average Updated FICO | item	747	736
Percent of Loans on Nonaccrual Status	2.08%	5.54%
Residential real estate mortgages [Member] | Estimated Current LTV Greater Than 100% [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 20	$ 30
Weighted Average Updated FICO | item	709	713
Percent of Loans on Nonaccrual Status	14.50%	7.72%
Residential real estate mortgages [Member] | Origination Loan To Value Ratio 70% And Below [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 6,865	$ 5,913
Residential real estate mortgages [Member] | Origination Loan to Value Ratio Greater Than 70% Through 90% [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	2,260	2,408
Residential real estate mortgages [Member] | Origination Loan to Value Ratio Greater Than 90% Through 100% [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	9	13
Home equity loans and lines of credit [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 2,350	$ 2,735
Weighted Average Updated FICO | item	769	770
Utilization Rate	36.00%	39.00%
Percent of Loans on Nonaccrual Status	0.20%	0.18%
Home equity loans and lines of credit [Member] | Origination FICO Score 620 Through 679 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 13	$ 16
Home equity loans and lines of credit [Member] | Origination FICO Score 680 Through 739 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	432	498
Home equity loans and lines of credit [Member] | Origination FICO Score 740 And Above [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	1,905	2,221
Home equity loans and lines of credit [Member] | Year of origination Pre 2012 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	1,660	2,048
Home equity loans and lines of credit [Member] | Year of origination 2012 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	105	125
Home equity loans and lines of credit [Member] | Year of origination 2013 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	193	232
Home equity loans and lines of credit [Member] | Year of origination 2014 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	152	188
Home equity loans and lines of credit [Member] | Year of origination 2015 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	146	142
Home equity loans and lines of credit [Member] | Year of origination 2016 [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	94
Home equity loans and lines of credit [Member] | Estimated Current LTV 70% And Below [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 2,070	$ 2,277
Weighted Average Updated FICO | item	771	772
Utilization Rate	35.00%	37.00%
Percent of Loans on Nonaccrual Status	0.12%	0.09%
Home equity loans and lines of credit [Member] | Estimated Current LTV Greater Than 70% through 90% [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 234	$ 373
Weighted Average Updated FICO | item	757	760
Utilization Rate	50.00%	50.00%
Percent of Loans on Nonaccrual Status	0.40%	0.48%
Home equity loans and lines of credit [Member] | Estimated Current LTV Greater Than 90% through 100% [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 29	$ 48
Weighted Average Updated FICO | item	747	748
Utilization Rate	66.00%	63.00%
Percent of Loans on Nonaccrual Status	1.74%	1.02%
Home equity loans and lines of credit [Member] | Estimated Current LTV Greater Than 100% [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 17	$ 37
Weighted Average Updated FICO | item	728	739
Utilization Rate	70.00%	67.00%
Percent of Loans on Nonaccrual Status	3.73%	1.79%
Home equity loans and lines of credit [Member] | Origination Loan To Value Ratio 70% And Below [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 1,628	$ 1,858
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	709	860
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	17
Pledged asset lines [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	3,851	3,232
Pledged asset lines [Member] | Weighted Average Loan to Value Ratio =70% [Member]
Financing Receivable, Recorded Investment [Line Items]
Balance	$ 3,851	$ 3,232
Weighted Average Updated FICO | item	763	764
Utilization Rate	46.00%	49.00%