Loans and Allowance for Loan Losses - Additional Information (Detail) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2014 Category	Mar. 31, 2013	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchased non-covered loans	$ 437,300,000		$ 448,800,000
Covered loans acquired in FDIC-assisted transactions	372,700,000	460,700,000	390,200,000
Number of risk grading system category	9
Modified loans	6,300,000	27,400,000
Troubled debt restructurings	21,200,000	23,300,000	20,900,000
Troubled debt restructurings, previous charge-offs	2,300,000	2,600,000	2,100,000
Allowance for loan losses allocated to troubled debt restructurings	422,000	591,000	432,000
Commitments to lend additional funds	0
Troubled debt restructurings, provision for loan loss expense	225,000	320,000	1,500,000
Non-Covered Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructurings	6,500,000		7,200,000
Troubled debt restructurings, previous charge-offs	345,000		0
Commitments to lend additional funds	0
Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	59,781,000	98,515,000	69,152,000
Modified loans	24,249,000	20,603,000	20,990,000
Troubled debt restructurings	22,775,000	21,592,000	22,243,000
Troubled debt restructurings, previous charge-offs	3,200,000	6,600,000	1,600,000
Commitments to lend additional funds	0
Minimum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past due loan accrued	90 days
Nonaccrual loans	200,000
Loan-to-value ratio	110.00%
Minimum [Member] | Troubled Debt Restructuring [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 100,000