Associate (Employee) Benefit Plans - Schedule of Net Periodic Benefit Cost Components of Postretirement Benefits (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Postemployment Benefits [Abstract]
Service cost	$ 14	$ 14	$ 29	$ 29
Interest cost	19	22	38	44
Prior service cost amortization	(19)	(19)	(26)	(38)
Net gain recognition	(16)	(5)	(31)	(10)
Net periodic benefit cost	$ (2)	$ 12	$ 10	$ 25