Loans - Summary of Impaired Financial Receivables Excluding Purchased Non-Covered and Covered Loans (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]
Troubled debt restructurings not included above	$ 21,100,000	$ 20,600,000	$ 20,900,000
Excluding Purchased Non-Covered and Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	22,111,000	31,811,000	29,203,000
Troubled debt restructurings not included above	17,337,000	18,015,000	17,214,000
Total impaired loans	39,448,000	49,826,000	46,417,000
Impaired loans not requiring a related allowance
Impaired loans requiring a related allowance	39,448,000	49,826,000	46,417,000
Allowance related to impaired loans	3,619,000	5,072,000	3,871,000
Average investment in impaired loans	43,814,000	54,481,000	51,721,000
Interest income recognized on impaired loans	42,000	451,000	522,000
Foregone interest income on impaired loans	$ 23,000	$ 172,000	$ 418,000