Pension and Other Postretirement Benefits (Tables)

3 Months Ended

Mar. 31, 2017

Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]

Schedule of Net Benefit Costs

The net periodic benefit cost for the three months ended March 31, 2017 and 2016 includes the following components: 

	Pension Benefits						Postretirement Benefits
	Three Months Ended   March 31,						Three Months Ended   March 31,
Components of Net Periodic Benefit Cost	2017			2016			2017			2016
Service cost	$	6,700		$	6,375		$	575		$	575
Interest cost	7,000			7,125			700			775
Expected return on plan assets	(7,725		)	(6,775		)	—			—
Amortization of:
Net actuarial loss	5,300			4,950			225			200
Prior service cost (gain)	100			100			(550		)	(550		)
Net periodic benefit cost	$	11,375		$	11,775		$	950		$	1,000