Postretirement Medical Plan (Tables)

9 Months Ended

Sep. 30, 2017

Postretirement Medical Plan

Schedule of components of net periodic postretirement benefit cost

		Three Months Ended				Nine Months Ended
		September 30,				September 30,
		2017		2016		2017		2016
Service cost		$	223	$	269	$	670	$	1,956
Interest cost			230		185		689		1,002
Amortization of prior service cost (credit)			(1,821)		(1,872)		(5,462)		(3,381)
	Net periodic benefit cost (credit)	$	(1,368)	$	(1,418)	$	(4,103)	$	(423)