Employee Retirement Plans - Schedule of Net Periodic Benefit Cost (Detail) - Defined Benefit Pension Plan [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Components of net periodic benefit cost:
Service cost	$ 444	$ 452	$ 888	$ 904
Interest cost	84	158	168	316
Expected return on plan assets	(68)	(117)	(136)	(234)
Prior service cost		3	0	6
Unrecognized net loss	24	1	48	2
Net periodic benefit cost	$ 484	$ 497	$ 968	$ 994