Pension and Other Postretirement Benefits (Tables)

6 Months Ended

Jun. 30, 2018

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

Schedule of Net Benefit Costs

The net periodic benefit cost for the three and six months ended June 30, 2018 and 2017 includes the following components: 

	Pension Benefits						Postretirement Benefits
	Three Months Ended   June 30,						Three Months Ended   June 30,
Components of Net Periodic Benefit Cost	2018			2017			2018			2017
Selling, general, and administrative expenses:
Service cost	$	7,167		$	6,508		$	584		$	588
Total selling, general, and administrative expenses	$	7,167		$	6,508		$	584		$	588
Non-operating expenses:
Interest cost	6,686			6,909			669			722
Expected return on plan assets	(7,856		)	(7,590		)	—			—
Amortization of:
Net actuarial loss	6,522			5,451			201			169
Prior service cost (gain)	84			110			(478		)	(540		)
Total non-operating expenses	$	5,436		$	4,880		$	392		$	351
Net periodic benefit cost	$	12,603		$	11,388		$	976		$	939

	Pension Benefits						Postretirement Benefits
	Six Months Ended   June 30,						Six Months Ended   June 30,
Components of Net Periodic Benefit Cost	2018			2017			2018			2017
Selling, general, and administrative expenses:
Service cost	$	14,267		$	13,208		$	1,159		$	1,163
Total selling, general, and administrative expenses	$	14,267		$	13,208		$	1,159		$	1,163
Non-operating expenses:
Interest cost	13,661			13,909			1,319			1,422
Expected return on plan assets	(15,931		)	(15,315		)	—			—
Amortization of:
Net actuarial loss	13,247			10,751			426			394
Prior service cost (gain)	159			210			(978		)	(1,090		)
Total non-operating expenses	$	11,136		$	9,555		$	767		$	726
Net periodic benefit cost	$	25,403		$	22,763		$	1,926		$	1,889