Loans Loans - Purchased, Sold and Reclassified to Held-for-Sale (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Retained Loans Purchases Sales And Transfer Into Held For Sale By Portfolio Segment [Line Items]
Financing Receivable, Significant Purchases	$ 2,720	$ 2,080
Financing Receivable, Significant Sales	2,582	1,220
Financing Receivable, Reclassification to Held-for-Sale	344	985
Consumer, excluding credit card
Retained Loans Purchases Sales And Transfer Into Held For Sale By Portfolio Segment [Line Items]
Financing Receivable, Significant Purchases	2,625	1,759
Financing Receivable, Significant Sales	1,429	357
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	0	923
Wholesale
Retained Loans Purchases Sales And Transfer Into Held For Sale By Portfolio Segment [Line Items]
Financing Receivable, Significant Purchases	95	321
Financing Receivable, Significant Sales	1,153	863
Financing Receivable, Reclassification to Held-for-Sale	$ 344	$ 62