Purchased Loans (Purchase Loan Balances) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Financing Receivable, Impaired [Line Items]
Purchased Impaired Loans - Outstanding Balance	$ 3,743	$ 3,933
Purchased Impaired Loans - Recorded Investment	3,380	3,522	$ 4,675
Purchased Impaired Loans - Carrying Value	3,068	3,212
Residential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Purchased Impaired Loans - Outstanding Balance	1,843	1,915
Total commercial lending [Member]
Financing Receivable, Impaired [Line Items]
Purchased Impaired Loans - Outstanding Balance	206	249
Purchased Impaired Loans - Recorded Investment	149	169	276
Purchased Impaired Loans - Carrying Value	99	120
Total commercial lending [Member] | Commercial [Member]
Financing Receivable, Impaired [Line Items]
Purchased Impaired Loans - Outstanding Balance	78	94
Purchased Impaired Loans - Recorded Investment	29	36
Purchased Impaired Loans - Carrying Value	18	24
Total commercial lending [Member] | Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Purchased Impaired Loans - Outstanding Balance	128	155
Purchased Impaired Loans - Recorded Investment	120	133
Purchased Impaired Loans - Carrying Value	81	96
Total consumer lending [Member]
Financing Receivable, Impaired [Line Items]
Purchased Impaired Loans - Outstanding Balance	3,537	3,684
Purchased Impaired Loans - Recorded Investment	3,231	3,353	$ 4,399
Purchased Impaired Loans - Carrying Value	2,969	3,092
Total consumer lending [Member] | Consumer [Member]
Financing Receivable, Impaired [Line Items]
Purchased Impaired Loans - Outstanding Balance	1,694	1,769
Purchased Impaired Loans - Recorded Investment	1,338	1,407
Purchased Impaired Loans - Carrying Value	1,313	1,392
Total consumer lending [Member] | Residential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Purchased Impaired Loans - Outstanding Balance	1,843	1,915
Purchased Impaired Loans - Recorded Investment	1,893	1,946
Purchased Impaired Loans - Carrying Value	$ 1,656	$ 1,700