Employee Benefit Plans - Schedule of Restricted Stock Awards Including Restricted Stock Units (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Nonvested Restricted Stock Activity
Shares, Non-vested at beginning of year	179,300	0
Shares, Granted	67,047	200,200
Shares, Vested	(75,283)	(12,500)
Shares, Forfeited	(8,258)	(8,400)
Shares, Non-vested outstanding at end of period	162,806	179,300
Available to grant	349,411,000	408,200
Nonvested Restricted Stock Activity, Weighted Average Grant Date Fair Value
Weighted Average Grant Date Fair Value, Non-vested at beginning of year	$ 21.20	$ 0.00
Weighted Average Grant Date Fair Value, Granted	34.77	21.17
Weighted Average Grant Date Fair Value, Vested	21.15	20.95
Weighted Average Grant Date Fair Value, Forfeited	29.51	20.95
Weighted Average Grant Date Fair Value, Non-vested at end of year	$ 26.39	$ 21.20