Retirement Plans - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Employer contribution	6.00%
Employee contribution	80.00%
Plan expense	$ 2,500,000	$ 2,700,000	$ 2,600,000
Retirement Plan expense	0	$ 0
Minimum [Member]
Total annual compensation for a calendar year for non-qualified deferred compensation plan	$ 110,000
Eligibility of participants	1.00%
Maximum [Member]
Eligibility of participants	25.00%