Loans and Allowance for Credit Losses - Schedule of Risk Category of Loans (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Commercial Loan [Member]
Risk Category Of Loans [Line Items]
Total	$ 1,397,882	$ 1,336,820
Commercial Loan [Member] | Pass [Member]
Risk Category Of Loans [Line Items]
Total	1,238,749	1,237,274
Commercial Loan [Member] | Grade Criticized [Member]
Risk Category Of Loans [Line Items]
Total	109,873	38,476
Commercial Loan [Member] | Substandard [Member]
Risk Category Of Loans [Line Items]
Total	17,852	23,388
Commercial Loan [Member] | Doubtful [Member]
Risk Category Of Loans [Line Items]
Total	31,408	37,682
Commercial Real Estate Construction Financing Receivable [Member]
Risk Category Of Loans [Line Items]
Total	85,283	99,081
Commercial Real Estate Construction Financing Receivable [Member] | Pass [Member]
Risk Category Of Loans [Line Items]
Total	64,912	62,604
Commercial Real Estate Construction Financing Receivable [Member] | Grade Criticized [Member]
Risk Category Of Loans [Line Items]
Total	9,383	11,969
Commercial Real Estate Construction Financing Receivable [Member] | Substandard [Member]
Risk Category Of Loans [Line Items]
Total	3,749	10,204
Commercial Real Estate Construction Financing Receivable [Member] | Doubtful [Member]
Risk Category Of Loans [Line Items]
Total	7,239	14,304
Commercial Real Estate Other Receivable [Member]
Risk Category Of Loans [Line Items]
Total	1,112,714	1,156,802
Commercial Real Estate Other Receivable [Member] | Pass [Member]
Risk Category Of Loans [Line Items]
Total	958,349	965,967
Commercial Real Estate Other Receivable [Member] | Grade Criticized [Member]
Risk Category Of Loans [Line Items]
Total	33,545	62,819
Commercial Real Estate Other Receivable [Member] | Substandard [Member]
Risk Category Of Loans [Line Items]
Total	45,428	38,252
Commercial Real Estate Other Receivable [Member] | Doubtful [Member]
Risk Category Of Loans [Line Items]
Total	$ 75,392	$ 89,764