Pension and Postretirement Benefits (Tables)

6 Months Ended

Jun. 30, 2018

General Discussion Of Pension And Other Postretirement Benefits [Abstract]

Schedule of Defined Benefit Plans Disclosures [Table Text Block]

	Three Months Ended June 30,								Six Months Ended June 30,
					Other								Other
					Postretirement								Postretirement
	Pension Benefits				Benefits				Pension Benefits				Benefits
		2018		2017		2018		2017		2018		2017		2018		2017
Service cost	$	960	$	871	$	3	$	1	$	1,948	$	1,789	$	5	$	4
Interest cost		1,032		1,003		33		39		2,081		2,011		66		72
Expected return on plan assets		(1,274)		(1,255)		—		—		(2,564)		(2,581)		—		—
Settlement charge		—		1,860		—		—		—		1,860		—		—
Actuarial loss amortization		793		792		14		22		1,593		1,661		29		27
Prior service cost amortization		(29)		(25)		—		—		(60)		(48)		—		—
Net periodic benefit cost	$	1,482	$	3,246	$	50	$	62	$	2,998	$	4,692	$	100	$	103