Retirement Benefits (Tables)

9 Months Ended

Sep. 30, 2019

Retirement Benefits [Abstract]

Components of Net Periodic Benefit Cost

The components of the net periodic pension benefit credit were as follows:

	Three Months Ended						Nine Months Ended
	Sept. 30, 2019			Sept. 30, 2018			Sept. 30, 2019			Sept. 30, 2018
	(Dollars in thousands)
Service cost	$	2,871		$	3,411		$	9,383		$	10,842
Interest cost	7,149			6,348			21,241			18,953
Expected return on plan assets	(15,200		)	(17,137		)	(45,425		)	(51,382		)
Amortization of prior service cost	46			34			86			103
Amortization of actuarial losses	4,084			1,877			12,324			5,450
Net periodic benefit credit	$	(1,050	)	$	(5,467	)	$	(2,391	)	$	(16,034	)

The components of the net periodic other postretirement benefit (credit) cost were as follows:

	Three Months Ended						Nine Months Ended
	Sept. 30, 2019			Sept. 30, 2018			Sept. 30, 2019			Sept. 30, 2018
	(Dollars in thousands)
Service cost	$	16		$	15		$	60		$	78
Interest cost	200			158			569			483
Amortization of prior service (credit) cost	(586		)	561			(1,749		)	(738		)
Amortization of actuarial gains	(33		)	(167		)	(366		)	(405		)
Net periodic benefit (credit) cost	$	(403	)	$	567		$	(1,486	)	$	(582	)