Contingent Liabilities and Commitments with Off-Balance Sheet Risk - Summary of Minimum Future Contractual Obligation Under Renewal of Contract (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012
Commitments And Contingencies Disclosure [Abstract]
2013	$ 11,016
2014	8,568
2015	6,120
2016	$ 3,672