Employee Benefit Plans - Additional Information (Detail) - USD ($) shares in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Discretionary profit sharing	$ 0	$ 0	$ 0
Settlement loss	(103,000)
Benefit cost, net periodic benefit cost	263,000	167,000	154,000
Estimated net loss from restoration plan, that will be amortized into periodic costs	100,000
Accumulated benefit obligation and projected benefit obligation	1,100,000	$ 1,200,000
Expected cash contribution	$ 200,000
Contribution plan, employer matching contribution percentage	50.00%
Defined contribution plans employee contribution percentage of eligible compensation matched by employer	6.00%
Shares allocated to the employee stock ownership plan	0.8	1.0
Contribution expense under employee stock ownership plan	$ 5,000,000	$ 4,600,000	4,300,000
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0
Discretionary profit sharing	7,600,000	$ 100,000	$ 300,000
Settlement loss	9,800,000
Benefit cost, net periodic benefit cost	$ 11,600,000