Securities (Detail) - Narrative	12 Months Ended
	Dec. 31, 2015 USD ($) security	Dec. 31, 2014 USD ($) security	Dec. 31, 2013 USD ($) security
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities pledged as collateral	$ 856,900,000	$ 779,400,000
Held-to-maturity securities pledged as collateral	0	0
Net realized gains on sales of securities	$ 2,373,000	$ 8,125,000	$ 34,572,000
Number Of CMOs Sold | security	1
Carrying Value Of CMO Sold	$ 1,300,000
Number of CDOs sold | security		1	1
Carrying value of CDO sold		$ 1,300,000	$ 0
Other Mortgage Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Net realized gains on sales of securities	1,900,000
Available-for-sale securities, excluding other mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Net realized gains on sales of securities	$ 521,000
Trust-preferred Collateralized Debt Obligations
Schedule of Available-for-sale Securities [Line Items]
Net realized gains on sales of securities		3,500,000
Available-for-sale securities, excluding collateralized debt obligations
Schedule of Available-for-sale Securities [Line Items]
Net realized gains on sales of securities		$ 4,600,000
Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Net realized gains on sales of securities			$ 34,000,000