Derivative Instruments and Hedging Activities - Gains (Losses) Related to Interest Rate Derivatives Designated as Hedges of Fair Value (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Gain Loss On Fair Value Hedges Recognized In Earnings [Line Items]
Gains (losses) on derivatives	$ (297)	$ 38
Designated as Fair Value Hedge | Interest Income | Interest Rate Swaps
Gain Loss On Fair Value Hedges Recognized In Earnings [Line Items]
Gains (losses) on derivatives	(99)	(54)
Designated as Fair Value Hedge | Interest Income | Loans and Long-term Borrowings | Derivatives designated as hedging instruments:
Gain Loss On Fair Value Hedges Recognized In Earnings [Line Items]
Gains (losses) on derivatives	99	54
Designated as Fair Value Hedge | Interest Expense | Interest Rate Swaps
Gain Loss On Fair Value Hedges Recognized In Earnings [Line Items]
Gains (losses) on derivatives	4,728	2,741
Designated as Fair Value Hedge | Interest Expense | Loans and Long-term Borrowings | Derivatives designated as hedging instruments:
Gain Loss On Fair Value Hedges Recognized In Earnings [Line Items]
Gains (losses) on derivatives	$ (4,719)	$ (2,781)