Employee Benefits

6 Months Ended

Jun. 30, 2018

Retirement Benefits [Abstract]

Employee Benefits

EMPLOYEE BENEFITS

Net Periodic Benefit Cost

The components of the net periodic benefit cost for our pension and postretirement benefit plans are as follows:

	Pension Plan						Postretirement Benefit Plan
Three Months Ended June 30,	2018			2017			2018			2017
Net periodic benefit cost
Service cost	$	2,175		$	1,714		$	750		$	505
Interest cost	1,875			1,765			502			482
Expected return on plan assets	(2,626		)	(2,412		)	—			—
Amortization of prior service credit	—			—			(1,352		)	(1,352		)
Amortization of net loss	1,072			891			589			461
Net periodic benefit cost	$	2,496		$	1,958		$	489		$	96

	Pension Plan						Postretirement Benefit Plan
Six Months Ended June 30,	2018			2017			2018			2017
Net periodic benefit cost
Service cost	$	4,350		$	3,427		$	1,499		$	1,010
Interest cost	3,750			3,530			1,004			964
Expected return on plan assets	(5,251		)	(4,824		)	—			—
Amortization of prior service credit	—			—			(2,704		)	(2,704		)
Amortization of net loss	2,143			1,782			1,178			922
Net periodic benefit cost	$	4,992		$	3,915		$	977		$	192

Employer Contributions

We previously disclosed in our Annual Report on Form 10-K for the year ended December 31, 2017 that we expected to contribute $6,400 to the pension plan in 2018. For the six-month period ended June 30, 2018, we contributed $3,200 to the pension plan.