Derivative Instruments - Amounts and Locations of Activity Related to Interest Rate Swaps Designated as Cash Flow Hedges within Corporation's Consolidated Balance Sheet and Statement of Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014 Interest Expense - Subordinated Debentures [Member]	Mar. 31, 2013 Interest Expense - Subordinated Debentures [Member]	Mar. 31, 2014 Other Income [Member]	Mar. 31, 2013 Other Income [Member]	Mar. 31, 2014 Accrued Interest and Other Liabilities [Member]	Dec. 31, 2013 Accrued Interest and Other Liabilities [Member]
Derivative [Line Items]
Interest rate contracts							$ (1,079)	$ (1,116)
Interest rate contracts	24	75
Interest expense, Fair Value			(97)	(97)
Other income					$ 0	$ 0