Securities - Summary of Cumulative Credit-Related OTTI Charges (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Beginning balance	$ 27	$ 27
Loss where impairment was not previously recognized	0	0
Additional loss where impairment was previously recognized	0	0
Reduction due to credit impaired securities sold	0	0
Ending balance	27	27
Equity Securities [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Beginning balance	27	27
Loss where impairment was not previously recognized	0	0
Additional loss where impairment was previously recognized	0	0
Reduction due to credit impaired securities sold	0	0
Ending balance	$ 27	$ 27