Associate (Employee) Benefit Plans - Schedule of Net Periodic Benefit Cost Components of Postretirement Benefits (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Business Acquisition [Line Items]
Service cost	$ 15	$ 15
Interest cost	19	19
Prior service cost amortization	(19)	(7)
Net gain recognition	(16)	(15)
Net periodic benefit cost	(1)	$ 12
Alliance
Business Acquisition [Line Items]
Service cost	10
Interest cost	75
Expected Return on Plan Assets	(135)
Prior service cost amortization	0
Net gain recognition	0
Net periodic benefit cost	$ (50)