Outstanding Balance of Loans Sold by Vintage and Type of Buyer (Detail) (USD $) In Billions, unless otherwise specified	Sep. 30, 2012
Outstanding balance remaining of loans sold to outside investors	$ 110.2
Agency Securities
Outstanding balance remaining of loans sold to outside investors	79.0	[1]
Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	18.0	[1]
Non Agency Securities [Member]
Outstanding balance remaining of loans sold to outside investors	13.2
Vintage 2005
Outstanding balance remaining of loans sold to outside investors	7.8
Vintage 2005 | Agency Securities
Outstanding balance remaining of loans sold to outside investors	3.4	[1]
Vintage 2005 | Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	0.7	[1]
Vintage 2005 | Non Agency Securities [Member]
Outstanding balance remaining of loans sold to outside investors	3.7
Vintage 2006
Outstanding balance remaining of loans sold to outside investors	9.8
Vintage 2006 | Agency Securities
Outstanding balance remaining of loans sold to outside investors	4.0	[1]
Vintage 2006 | Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	0.4	[1]
Vintage 2006 | Non Agency Securities [Member]
Outstanding balance remaining of loans sold to outside investors	5.4
Vintage 2007
Outstanding balance remaining of loans sold to outside investors	12.2
Vintage 2007 | Agency Securities
Outstanding balance remaining of loans sold to outside investors	7.7	[1]
Vintage 2007 | Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	0.4	[1]
Vintage 2007 | Non Agency Securities [Member]
Outstanding balance remaining of loans sold to outside investors	4.1
Vintage 2008
Outstanding balance remaining of loans sold to outside investors	9.9
Vintage 2008 | Agency Securities
Outstanding balance remaining of loans sold to outside investors	7.7	[1]
Vintage 2008 | Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	2.2	[1]
Vintage 2008 | Non Agency Securities [Member]
Outstanding balance remaining of loans sold to outside investors	0
Vintage 2009
Outstanding balance remaining of loans sold to outside investors	23.2
Vintage 2009 | Agency Securities
Outstanding balance remaining of loans sold to outside investors	18.5	[1]
Vintage 2009 | Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	4.7	[1]
Vintage 2009 | Non Agency Securities [Member]
Outstanding balance remaining of loans sold to outside investors	0
Vintage 2010
Outstanding balance remaining of loans sold to outside investors	14.7
Vintage 2010 | Agency Securities
Outstanding balance remaining of loans sold to outside investors	11.2	[1]
Vintage 2010 | Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	3.5	[1]
Vintage 2010 | Non Agency Securities [Member]
Outstanding balance remaining of loans sold to outside investors	0
Vintage 2011
Outstanding balance remaining of loans sold to outside investors	14.4
Vintage 2011 | Agency Securities
Outstanding balance remaining of loans sold to outside investors	11.6	[1]
Vintage 2011 | Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	2.8	[1]
Vintage 2011 | Non Agency Securities [Member]
Outstanding balance remaining of loans sold to outside investors	0
Vintage 2012
Outstanding balance remaining of loans sold to outside investors	18.2
Vintage 2012 | Agency Securities
Outstanding balance remaining of loans sold to outside investors	14.9	[1]
Vintage 2012 | Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	3.3	[1]
Vintage 2012 | Non Agency Securities [Member]
Outstanding balance remaining of loans sold to outside investors	$ 0

[1] Balances based on loans serviced by the Company.