Derivative Financial Instruments - Summary of Net Losses on Derivatives and Hedging Activities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivatives designated as hedging instruments:
Total net gain (loss) related to fair value hedge ineffectiveness	$ 0	$ 0	$ 0
Derivatives not designated as hedging instruments:
Total net gains (losses) related to derivatives not designated as hedging instruments	(1)	(1)	(9)
Net gains (losses) on derivatives and hedging activities	(1)	(1)	(9)
Interest Rate Swaps [Member]
Derivatives designated as hedging instruments:
Total net gain (loss) related to fair value hedge ineffectiveness	0	0	0
Interest Rate Caps/Floors [Member]
Derivatives not designated as hedging instruments:
Total net gains (losses) related to derivatives not designated as hedging instruments	$ (1)	$ (1)	$ (9)