Components of Net Periodic Benefit Cost (Tables)

9 Months Ended

Sep. 30, 2018

Retirement Benefits [Abstract]

Schedule of Net Benefit Costs

	Three Months Ended September 30,										Nine Months Ended September 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	$	1,041		$	1,074		$	31	$	40
Interest cost	798			905			33		43		2,395			2,716			98		129
Expected return on plan assets	(991		)	(985		)	—		—		(2,972		)	(2,955		)	—		—
Net amortization of prior service cost	—			—			—		—		1			1			—		—
Net amortization of net (gain) loss	362			301			—		—		1,085			903			—		—
Net Periodic Benefit Cost	$	516		$	579		$	43	$	56	$	1,550		$	1,739		$	129	$	169