Securities - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) Securities	Dec. 31, 2014 USD ($) Securities	Dec. 31, 2013 USD ($)
Investments, Debt and Equity Securities [Abstract]
Number of securities holdings | Securities	0	0
Shareholders' equity percentage	10.00%	10.00%
Securities	$ 312,669	$ 325,799
Tax provision related to net realized gains	233	150	$ 124
Proceeds from sale of trading securities	2,129	248	5,811
Net realized (losses) gains on trading securities	$ (211)	$ 10	$ 579