Pension and Postretirement Benefits (Tables)

3 Months Ended

Mar. 31, 2018

General Discussion Of Pension And Other Postretirement Benefits [Abstract]

Schedule of Defined Benefit Plans Disclosures [Table Text Block]

	Three Months Ended March 31,
					Other
	Pension Benefits				Postretirement Benefits
		2018		2017		2018		2017
Service cost	$	988	$	918	$	2	$	3
Interest cost		1,049		1,008		33		33
Expected return on plan assets		(1,290)		(1,326)		—		—
Actuarial loss amortization		800		869		15		5
Prior service cost amortization		(31)		(23)		—		—
Total net periodic benefit cost	$	1,516	$	1,446	$	50	$	41