Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Accounting Policies [Abstract]
Interest bearing amounts held at other financial institutions	$ 109.5	$ 177.3	$ 109.5	$ 177.3
Dilutive effect of common stock issuable upon exercise of options, shares	394,738	370,227	362,517	405,702
Anti-dilutive shares			637,331	495,366