Outstanding Balance of Loans Sold by Vintage and Type of Buyer (Detail) (USD $) In Billions, unless otherwise specified	Mar. 31, 2013
Outstanding balance remaining of loans sold to outside investors	$ 107.4
US Government Sponsored Agency [Member]
Outstanding balance remaining of loans sold to outside investors	77.8	[1]
Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	17.1	[1]
Non Government Sponsored Agency [Member]
Outstanding balance remaining of loans sold to outside investors	12.5
Vintage 2005
Outstanding balance remaining of loans sold to outside investors	6.8
Vintage 2005 | US Government Sponsored Agency [Member]
Outstanding balance remaining of loans sold to outside investors	2.7	[1]
Vintage 2005 | Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	0.5	[1]
Vintage 2005 | Non Government Sponsored Agency [Member]
Outstanding balance remaining of loans sold to outside investors	3.6
Vintage 2006
Outstanding balance remaining of loans sold to outside investors	8.7
Vintage 2006 | US Government Sponsored Agency [Member]
Outstanding balance remaining of loans sold to outside investors	3.2	[1]
Vintage 2006 | Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	0.3	[1]
Vintage 2006 | Non Government Sponsored Agency [Member]
Outstanding balance remaining of loans sold to outside investors	5.2
Vintage 2007
Outstanding balance remaining of loans sold to outside investors	10.3
Vintage 2007 | US Government Sponsored Agency [Member]
Outstanding balance remaining of loans sold to outside investors	6.2	[1]
Vintage 2007 | Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	0.4	[1]
Vintage 2007 | Non Government Sponsored Agency [Member]
Outstanding balance remaining of loans sold to outside investors	3.7
Vintage 2008
Outstanding balance remaining of loans sold to outside investors	7.5
Vintage 2008 | US Government Sponsored Agency [Member]
Outstanding balance remaining of loans sold to outside investors	5.9	[1]
Vintage 2008 | Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	1.6	[1]
Vintage 2008 | Non Government Sponsored Agency [Member]
Outstanding balance remaining of loans sold to outside investors	0
Vintage 2009
Outstanding balance remaining of loans sold to outside investors	18.2
Vintage 2009 | US Government Sponsored Agency [Member]
Outstanding balance remaining of loans sold to outside investors	14.4	[1]
Vintage 2009 | Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	3.8	[1]
Vintage 2009 | Non Government Sponsored Agency [Member]
Outstanding balance remaining of loans sold to outside investors	0
Vintage 2010
Outstanding balance remaining of loans sold to outside investors	12.0
Vintage 2010 | US Government Sponsored Agency [Member]
Outstanding balance remaining of loans sold to outside investors	9.1	[1]
Vintage 2010 | Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	2.9	[1]
Vintage 2010 | Non Government Sponsored Agency [Member]
Outstanding balance remaining of loans sold to outside investors	0
Vintage 2011
Outstanding balance remaining of loans sold to outside investors	12.2
Vintage 2011 | US Government Sponsored Agency [Member]
Outstanding balance remaining of loans sold to outside investors	9.8	[1]
Vintage 2011 | Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	2.4	[1]
Vintage 2011 | Non Government Sponsored Agency [Member]
Outstanding balance remaining of loans sold to outside investors	0
Vintage 2012
Outstanding balance remaining of loans sold to outside investors	23.5
Vintage 2012 | US Government Sponsored Agency [Member]
Outstanding balance remaining of loans sold to outside investors	19.3	[1]
Vintage 2012 | Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	4.2	[1]
Vintage 2012 | Non Government Sponsored Agency [Member]
Outstanding balance remaining of loans sold to outside investors	0
Vintage 2013
Outstanding balance remaining of loans sold to outside investors	8.2
Vintage 2013 | US Government Sponsored Agency [Member]
Outstanding balance remaining of loans sold to outside investors	7.2	[1]
Vintage 2013 | Ginnie Mae
Outstanding balance remaining of loans sold to outside investors	1.0	[1]
Vintage 2013 | Non Government Sponsored Agency [Member]
Outstanding balance remaining of loans sold to outside investors	$ 0

[1] Balances based on loans currently serviced by the Company and excludes loans serviced by others and certain loans in foreclosure.