Loans and Allowance for Credit Losses - Schedule of Impaired Loans that are Individually Evaluated (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
Recorded Investment, Total commercial and CRE	$ 75,536	$ 77,237
Unpaid Principal Balance, Total commercial and CRE	89,364	94,262
Related Allowance	7,208	7,492
Commercial Loan [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment with no related allowance	12,646	6,563
Unpaid Principal Balance with no related allowance	13,938	9,280
Recorded Investment with related allowance	16,471	23,417
Unpaid Principal Balance with related allowance	21,326	28,574
Related Allowance	4,593	4,702
Commercial Real Estate Construction Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment with no related allowance	603	1,179
Unpaid Principal Balance with no related allowance	711	1,287
Recorded Investment with related allowance	2,844	3,227
Unpaid Principal Balance with related allowance	2,844	3,227
Related Allowance	69	69
Commercial Real Estate Other Receivable [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment with no related allowance	13,478	16,944
Unpaid Principal Balance with no related allowance	19,150	23,162
Recorded Investment with related allowance	29,494	25,907
Unpaid Principal Balance with related allowance	31,395	28,732
Related Allowance	$ 2,546	$ 2,721