Loans - Summary of Impaired Financial Receivables (Summary of Excluding Purchased Non-Covered and Covered Loans) (Detail) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructurings not included above	$ 21,200,000	$ 23,300,000	$ 20,900,000
Excluding Purchased Non-Covered and Covered Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	26,729,000	37,476,000	29,203,000
Troubled debt restructurings not included above	18,848,000	18,513,000	17,214,000
Total impaired loans	45,577,000	55,989,000	46,417,000
Impaired loans not requiring a related allowance
Impaired loans requiring a related allowance	45,577,000	55,989,000	46,417,000
Allowance related to impaired loans	4,324,000	4,839,000	3,871,000
Average investment in impaired loans	45,997,000	56,808,000	51,721,000
Interest income recognized on impaired loans	20,000	78,000	522,000
Foregone interest income on impaired loans	$ 246,000	$ 54,000	$ 418,000