Regulatory Capital and Other Regulatory Matters Regulatory Capital and Other Regulatory Matters (Common Share Repurchases) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Jan. 10, 2018	Dec. 31, 2015
Accelerated Share Repurchases [Line Items]
Treasury Stock, Value	$ 1,110	$ 357
Common Stock, Shares, Outstanding	437,053,936	467,000,306		481,980,111
Dividends Payable, Amount Per Share	$ 0.13		$ 0.13
Increase (Decrease) in Dividends Payable, per share	$ 0.01		$ 0.01
Assets	$ 167,148	$ 163,728		$ 158,581
Cash Dividends Paid to Parent Company	3,300	0
FRB Required Reserve Balance	370	149
Statutory Accounting Practices, Statutory Amount Available for Dividend Payments	87
Common Share Repurchases, Period One [Member]
Accelerated Share Repurchases [Line Items]
Treasury Stock, Value	$ 190
Treasury Stock, Common, Shares	7,033,000
Dividends Payable, Amount Per Share	$ 0.12
Common Share Repurchases, Period Two [Member]
Accelerated Share Repurchases [Line Items]
Treasury Stock, Value	$ 190
Treasury Stock, Common, Shares	8,507,000
Dividends Payable, Amount Per Share	$ 0.12
Common Share Repurchases, Period Three [Member]
Accelerated Share Repurchases [Line Items]
Treasury Stock, Value	$ 204
Treasury Stock, Common, Shares	10,485,000
Dividends Payable, Amount Per Share	$ 0.08
Common Share Repurchases, Period Four [Member]
Accelerated Share Repurchases [Line Items]
Treasury Stock, Value	$ 169
Treasury Stock, Common, Shares	8,097,000
Dividends Payable, Amount Per Share	$ 0.08
Common Share Repurchases, Period Five [Member]
Accelerated Share Repurchases [Line Items]
Treasury Stock, Value		$ 167
Treasury Stock, Common, Shares		8,745,000
Dividends Payable, Amount Per Share		$ 0.08
Common Share Repurchases, Period Six [Member]
Accelerated Share Repurchases [Line Items]
Treasury Stock, Value		$ 159
Treasury Stock, Common, Shares		8,298,000
Dividends Payable, Amount Per Share		$ 0.08
Beginning of Period [Member] | Common Share Repurchases, Period One [Member]
Accelerated Share Repurchases [Line Items]
Common Stock, Shares, Outstanding	443,796,000,000
Beginning of Period [Member] | Common Share Repurchases, Period Two [Member]
Accelerated Share Repurchases [Line Items]
Common Stock, Shares, Outstanding	452,292,000
Beginning of Period [Member] | Common Share Repurchases, Period Three [Member]
Accelerated Share Repurchases [Line Items]
Common Stock, Shares, Outstanding	462,193,000
Beginning of Period [Member] | Common Share Repurchases, Period Four [Member]
Accelerated Share Repurchases [Line Items]
Common Stock, Shares, Outstanding	467,000,000
Beginning of Period [Member] | Common Share Repurchases, Period Five [Member]
Accelerated Share Repurchases [Line Items]
Common Stock, Shares, Outstanding		475,470,000
Beginning of Period [Member] | Common Share Repurchases, Period Six [Member]
Accelerated Share Repurchases [Line Items]
Common Stock, Shares, Outstanding		483,753,000
End of Period [Member] | Common Share Repurchases, Period One [Member]
Accelerated Share Repurchases [Line Items]
Common Stock, Shares, Outstanding	437,053,936,000
End of Period [Member] | Common Share Repurchases, Period Two [Member]
Accelerated Share Repurchases [Line Items]
Common Stock, Shares, Outstanding	443,796,233,000
End of Period [Member] | Common Share Repurchases, Period Three [Member]
Accelerated Share Repurchases [Line Items]
Common Stock, Shares, Outstanding	452,292,000
End of Period [Member] | Common Share Repurchases, Period Four [Member]
Accelerated Share Repurchases [Line Items]
Common Stock, Shares, Outstanding	462,193,000
End of Period [Member] | Common Share Repurchases, Period Five [Member]
Accelerated Share Repurchases [Line Items]
Common Stock, Shares, Outstanding		467,000,000
End of Period [Member] | Common Share Repurchases, Period Six [Member]
Accelerated Share Repurchases [Line Items]
Common Stock, Shares, Outstanding		475,470,000
Subsidiaries [Member]
Accelerated Share Repurchases [Line Items]
Assets	$ 137,400	$ 123,500