Pension and Other Postretirement Benefits (Tables)

6 Months Ended

Jun. 30, 2018

Retirement Benefits [Abstract]

Schedule of Net Benefit Costs

Pension and other postretirement benefits expenses consisted of the following:

	Three months ended June 30,						Six months ended June 30,
Pensions	2018			2017			2018			2017
Service cost	$	1,398		$	1,459		$	2,988		$	3,102
Interest cost	4,383			4,666			8,692			9,287
Expected return on plan assets	(7,383		)	(6,816		)	(14,777		)	(13,676		)
Amortization of prior service cost	140			111			281			220
Amortization of actuarial losses	3,029			2,663			5,840			5,143
Curtailment gain	—			(7,217		)	—			(7,217		)
Settlement gain	—			(230		)	—			(491		)
Net periodic benefit cost	$	1,567		$	(5,364	)	$	3,024		$	(3,632	)

	Three months ended June 30,					Six months ended June 30,
Other Postretirement Benefits	2018		2017			2018		2017
Service cost	$	18	$	20		$	42	$	42
Interest cost	337		392			681		781
Amortization of prior service cost (credit)	5		(17		)	10		(34		)
Amortization of actuarial losses	126		70			286		139
Net periodic benefit cost	$	486	$	465		$	1,019	$	928