Derivative Instruments and Hedging Activities - Gains (Losses) on Interest Rate Derivatives Designated as Fair Value Hedges (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Gain Loss On Fair Value Hedges Recognized In Earnings [Line Items]
Gains (losses) on derivatives	$ (860)	$ (297)
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	97	(99)
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	(97)	99
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	0	4,728
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	$ 0	$ (4,719)