Employer Sponsored Benefit Plan - Plan Assets and Benefit Obligations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Change in benefit obligation:
Interest cost	$ 2,058	$ 2,139	$ 2,066
Change in plan assets:
Fair value of plan assets at beginning of year	37,038
Fair value of plan assets at end of year	44,174	37,038
Balance sheet amounts:
Noncurrent liabilities	(9,743)	(14,729)
Domestic Plan
Change in benefit obligation:
Net benefit obligation at beginning of year	50,086	48,081
Interest cost	2,058	2,139
Actuarial loss	2,126	2,062
Gross benefits paid	(2,388)	(2,196)
Net benefit obligation at end of year	51,882	50,086	48,081
Change in plan assets:
Fair value of plan assets at beginning of year	37,038	35,413
Actual return on plan assets	5,924	221
Contributions	3,600	3,600
Gross benefits paid	(2,388)	(2,196)
Fair value of plan assets at end of year	44,174	37,038	$ 35,413
Net benefit obligation in excess of plan assets	(7,708)	(13,048)
Balance sheet amounts:
Noncurrent liabilities	(7,708)	(13,048)
Total liabilities	(7,708)	(13,048)
Amounts recognized in accumulated other comprehensive income, net of tax consist of:
Net actuarial loss	17,632	19,689
Net amount recognized	$ 17,632	$ 19,689