Mortgage Servicing Rights - MSRs and Related Characteristics by Portfolio (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013 BasisPoint Y Multiple	Mar. 31, 2013	Dec. 31, 2012 BasisPoint Multiple Y	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011
Servicing Assets at Fair Value [Line Items]
Servicing portfolio	$ 223,904		$ 215,637
Fair value	2,377	1,955	1,700	1,594	1,737	1,519
Value (bps)	106		79
Weighted-average servicing fees (bps)	31		31
Multiple (value/servicing fees)	3.42		2.55
Weighted-average note rate	4.32%		4.54%
Weighted-average age (in years)	2.5		2.6
Weighted-average expected prepayment (constant prepayment rate)	12.80%		20.10%
Weighted-average expected life (in years)	6.2		4.2
Weighted-average discount rate	10.30%		10.40%
MRBP [Member]
Servicing Assets at Fair Value [Line Items]
Servicing portfolio	14,516		14,143
Fair value	160		154
Value (bps)	110		109
Weighted-average servicing fees (bps)	40		40
Multiple (value/servicing fees)	2.75		2.73
Weighted-average note rate	4.89%		5.13%
Weighted-average age (in years)	4.1		4.2
Weighted-average expected prepayment (constant prepayment rate)	12.80%		13.20%
Weighted-average expected life (in years)	6.2		6.1
Weighted-average discount rate	12.10%		12.10%
Government [Member]
Servicing Assets at Fair Value [Line Items]
Servicing portfolio	40,552		39,048
Fair value	429		314
Value (bps)	106		80
Weighted-average servicing fees (bps)	32		33
Multiple (value/servicing fees)	3.31		2.42
Weighted-average note rate	4.34%		4.57%
Weighted-average age (in years)	2.4		2.4
Weighted-average expected prepayment (constant prepayment rate)	14.20%		21.20%
Weighted-average expected life (in years)	5.9		4.2
Weighted-average discount rate	11.30%		11.40%
Conventional [Member]
Servicing Assets at Fair Value [Line Items]
Servicing portfolio	168,836		162,446
Fair value	$ 1,788		$ 1,232
Value (bps)	106		76
Weighted-average servicing fees (bps)	30		30
Multiple (value/servicing fees)	3.53		2.53
Weighted-average note rate	4.26%		4.48%
Weighted-average age (in years)	2.4		2.5
Weighted-average expected prepayment (constant prepayment rate)	12.50%		20.40%
Weighted-average expected life (in years)	6.3		4.1
Weighted-average discount rate	9.90%		10.00%