Loans - Purchased, Sold and Reclassified to Held-for-Sale (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Retained Loans Purchases Sales and Transfer Into Held For Sale By Portfolio Segment [Line Items]
Financing Receivable, Significant Purchases	$ 7,428	$ 8,431
Financing Receivable, Significant Sales	5,275	4,673
Financing Receivable, Reclassification to Held-for-Sale	1,547	2,544
Consumer, Excluding Credit Card
Retained Loans Purchases Sales and Transfer Into Held For Sale By Portfolio Segment [Line Items]
Financing Receivable, Significant Purchases	6,601	7,525
Financing Receivable, Significant Sales	1,852	1,384
Financing Receivable, Reclassification to Held-for-Sale	0	0
Credit Card
Retained Loans Purchases Sales and Transfer Into Held For Sale By Portfolio Segment [Line Items]
Financing Receivable, Significant Purchases	0	0
Financing Receivable, Significant Sales	0	0
Financing Receivable, Reclassification to Held-for-Sale	1,043	2,006
Wholesale
Retained Loans Purchases Sales and Transfer Into Held For Sale By Portfolio Segment [Line Items]
Financing Receivable, Significant Purchases	827	906
Financing Receivable, Significant Sales	3,423	3,289
Financing Receivable, Reclassification to Held-for-Sale	$ 504	$ 538