Unpaid Principal Balances of Loans Serviced (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Servicing Assets at Fair Value [Line Items]
Unpaid principle balance of loans serviced	$ 347,358	$ 431,633
Freddie Mac
Servicing Assets at Fair Value [Line Items]
Unpaid principle balance of loans serviced	304,831	368,518
Fannie Mae
Servicing Assets at Fair Value [Line Items]
Unpaid principle balance of loans serviced	29,196	44,948
Federal Home Loan Bank
Servicing Assets at Fair Value [Line Items]
Unpaid principle balance of loans serviced	11,578	16,241
Other investors
Servicing Assets at Fair Value [Line Items]
Unpaid principle balance of loans serviced	$ 1,753	$ 1,926