Loans - Additional Information (Detail) (USD $)	6 Months Ended		12 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchased non-covered loans	$ 702,100,000	$ 0	$ 448,800,000
Covered loans acquired in FDIC-assisted transactions	331,300,000	443,500,000	390,200,000
Modified loans	8,400,000	20,700,000
Troubled debt restructurings	21,100,000	20,600,000	20,900,000
Troubled debt restructurings, previous charge-offs	3,000,000	2,000,000	2,100,000
Allowance for loan losses allocated to troubled debt restructurings	398,000	482,000	432,000
Commitments to lend additional funds	0
Troubled debt restructuring, amount defaulted	130,218
Troubled debt restructurings, provision for loan loss expense	593,000	790,000	1,500,000
Minimum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	100,000
Loan-to-value ratio	110.00%
Minimum [Member] | Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 200,000