Borrowed Funds - Schedule of Repayment of Long-Term Borrowings for Securities Sold Under Agreements to Repurchase (Detail) (Long-term borrowings [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Long-term borrowings [Member]
Debt Instrument [Line Items]
2016	$ 92,500
2017	220,000
2018	100,000
2019	50,000
Securities sold under agreements to repurchase	$ 462,500	$ 587,500