Pension and Postretirement Benefits (Tables)

9 Months Ended

Sep. 30, 2018

General Discussion Of Pension And Other Postretirement Benefits [Abstract]

Schedule of Defined Benefit Plans Disclosures [Table Text Block]

	Three Months Ended September 30,								Nine Months Ended September 30,
					Other								Other
					Postretirement								Postretirement
	Pension Benefits				Benefits				Pension Benefits				Benefits
		2018		2017		2018		2017		2018		2017		2018		2017
Service cost	$	938	$	921	$	—	$	2	$	2,886	$	2,710	$	5	$	6
Interest cost		1,015		994		31		36		3,096		3,005		97		108
Expected return on plan assets		(1,229)		(1,276)		—		—		(3,793)		(3,857)		—		—
Settlement charge		—		—		—		—		—		1,860		—		—
Actuarial loss amortization		782		798		2		13		2,375		2,459		31		40
Prior service cost amortization		(28)		(28)		—		—		(88)		(76)		—		—
Net periodic benefit cost	$	1,478	$	1,409	$	33	$	51	$	4,476	$	6,101	$	133	$	154