Employee Benefit Plans - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Percentage of employee's contribution to the plan up to 6% of base salary matched by the Company	100.00%
Employer's contribution percentage	6.00%
Employer's contribution	$ 3,000,000	$ 2,500,000	$ 2,200,000
401(k) Profit Sharing Plan Two [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer's contribution percentage	6.00%
Employer contribution to the plan for every $1.00 contributed by an employee	$ 0.25
Employee's contribution to the plan up to 6% of base salary by the company	$ 1.00