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		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Gain Loss On Fair Value Hedges Recognized In Earnings [Line Items]
Gains (losses) on derivatives	$ (92)	$ 70	$ (389)	$ 108
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	2	157	(97)	103
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	(2)	(157)	97	(103)
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	2,069	(3,832)	6,797	(1,091)
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	$ (2,060)	$ 3,840	$ (6,779)	$ 1,059