Banks and thrifts increased their holdings of first-lien residential mortgages in the first quarter of 2012 compared with a year ago, according to the Inside Mortgage Finance Bank Mortgage Database. The 3.0 percent growth rate was partly due to originations of nonconforming mortgages, which helped offset portfolio runoff. Banks and thrifts held $1.74 trillion in first-liens in portfolio at the end of the first quarter. Among the top three bank portfolio lenders, only Wells Fargo ... [Includes one data chart]