Goodwill and Other Intangible Assets - Summary of the Key Characteristics, Inputs, and Economic Assumptions Used to Estimate the Fair Value of the Company's MSRs (Detail) (USD $) In Millions, unless otherwise specified				12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Mortgage Servicing Rights, Fair Value [Member]	Dec. 31, 2011 Mortgage Servicing Rights, Fair Value [Member]
Intangible Assets, Net (Excluding Goodwill)	$ 956	$ 1,017	$ 1,571
Prepayment rate assumption (annual)				16.00%	20.00%
Decline in fair value from 10% adverse change				50	52
Decline in fair value from 20% adverse change				95	98
Discount rate (annual)				11.00%	11.00%
Decline in fair value from 10% adverse change				37	33
Decline in fair value from 20% adverse change				$ 70	$ 63
Weighted-average life (in years)				4 years 11 months	4 years 3 months
Weighted-average coupon				4.80%	5.20%