Outstanding Balance of Loans Sold by Vintage and Type of Buyer (Detail) (USD $) In Billions, unless otherwise specified	Mar. 31, 2012
Outstanding balance remaining of loans sold to outside investors	$ 114.3
Agency Securities
Outstanding balance remaining of loans sold to outside investors	82.6	[1]
Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	17.7	[1]
Non Agency Securities [Member]
Outstanding balance remaining of loans sold to outside investors	14.0
Vintage 2005
Outstanding balance remaining of loans sold to outside investors	8.7
Vintage 2005 | Agency Securities
Outstanding balance remaining of loans sold to outside investors	4.1	[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	3.9
Vintage 2006
Outstanding balance remaining of loans sold to outside investors	11.1
Vintage 2006 | Agency Securities
Outstanding balance remaining of loans sold to outside investors	4.9	[1]
Vintage 2006 | Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	0.5	[1]
Vintage 2006 | Non Agency Securities [Member]
Outstanding balance remaining of loans sold to outside investors	5.7
Vintage 2007
Outstanding balance remaining of loans sold to outside investors	14.6
Vintage 2007 | Agency Securities
Outstanding balance remaining of loans sold to outside investors	9.6	[1]
Vintage 2007 | Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	0.6	[1]
Vintage 2007 | Non Agency Securities [Member]
Outstanding balance remaining of loans sold to outside investors	4.4
Vintage 2008
Outstanding balance remaining of loans sold to outside investors	12.6
Vintage 2008 | Agency Securities
Outstanding balance remaining of loans sold to outside investors	10.0	[1]
Vintage 2008 | Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	2.6	[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	28.2
Vintage 2009 | Agency Securities
Outstanding balance remaining of loans sold to outside investors	22.7	[1]
Vintage 2009 | Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	5.5	[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	17.1
Vintage 2010 | Agency Securities
Outstanding balance remaining of loans sold to outside investors	13.2	[1]
Vintage 2010 | Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	3.9	[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	16.1
Vintage 2011 | Agency Securities
Outstanding balance remaining of loans sold to outside investors	13.1	[1]
Vintage 2011 | Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	3.0	[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	5.9
Vintage 2012 | Agency Securities
Outstanding balance remaining of loans sold to outside investors	5.0	[1]
Vintage 2012 | Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	0.9	[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.