Allowance for Credit Losses - Summary of Activity in Allowance for Loan Losses (Parenthetical) (Detail) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Covered loans charge-offs	$ 433		$ 1,200	$ 146
Covered loans recovered			462
Loans charged-off	2,345	12,006	21,335	32,081
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans charged-off	1,852	8,556	11,806	17,322
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans charged-off	181	947	6,703	7,329
Non-Performing Loans [Member] | Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans charged-off	4,800
Non-Performing Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans charged-off	$ 4,000