Long-Term Borrowings and Subordinated Debt - Schedule of Junior Subordinated Debt Securities and Interest Expense (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Junior Subordinated Debentures [Line Items]
Balance	$ 45,619	$ 45,619	$ 90,619
Interest Expense	1,222	2,070	2,915
2006 Junior Subordinated Debt [Member]
Junior Subordinated Debentures [Line Items]
Balance	25,000	25,000	25,000
Interest Expense	463	475	523
2008 Junior Subordinated Debt-Trust Preferred Securities [Member]
Junior Subordinated Debentures [Line Items]
Balance	20,619	20,619	20,619
Interest Expense	759	770	808
2008 Junior Subordinated Debt [Member]
Junior Subordinated Debentures [Line Items]
Balance	0	0	20,000
Interest Expense	0	422	818
2008 Junior Subordinated Debt [Member]
Junior Subordinated Debentures [Line Items]
Balance	0	0	25,000
Interest Expense	$ 0	$ 403	$ 766