Components of Net Periodic Benefit Cost (Tables)

6 Months Ended

Jun. 30, 2018

Retirement Benefits [Abstract]

Schedule of Net Benefit Costs

	Three Months Ended June 30,										Six Months Ended June 30,
	(000's)										(000's)
	Pension Benefits						Post-Retirement Health Benefits				Pension Benefits						Post-Retirement Health Benefits
	2018			2017			2018		2017		2018			2017			2018		2017
Service cost	$	347		$	358		$	10	$	13	$	694		$	716		$	21	$	26
Interest cost	798			905			33		43		1,597			1,810			65		86
Expected return on plan assets	(991		)	(985		)	—		—		(1,981		)	(1,970		)	—		—
Net amortization of prior service cost	—			—			—		—		—			—			—		—
Net amortization of net (gain) loss	362			301			—		—		723			602			—		—
Net Periodic Benefit Cost	$	516		$	579		$	43	$	56	$	1,033		$	1,158		$	86	$	112