Retirement Benefits

9 Months Ended

Sep. 30, 2017

Retirement Benefits [Abstract]

Retirement Benefits

Retirement Benefits

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

	Three Months Ended						Nine Months Ended
	Sept. 30, 2017			Sept. 30, 2016			Sept. 30, 2017			Sept. 30, 2016
	(Dollars in thousands)
Service cost	$	3,532		$	2,950		$	9,967		$	9,584
Interest cost	6,482			6,473			19,114			19,351
Expected return on plan assets	(15,832		)	(14,653		)	(47,258		)	(43,819		)
Amortization of prior service cost	75			113			235			415
Amortization of actuarial losses	1,501			2,326			5,208			6,493
Special termination benefits	—			—			—			2,900
Curtailment loss	—			—			—			180
Net periodic benefit credit	$	(4,242	)	$	(2,791	)	$	(12,734	)	$	(4,896	)

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

	Three Months Ended						Nine Months Ended
	Sept. 30, 2017			Sept. 30, 2016			Sept. 30, 2017			Sept. 30, 2016
	(Dollars in thousands)
Service cost	$	9		$	52		$	79		$	188
Interest cost	168			230			520			737
Amortization of prior service credit	(857		)	(816		)	(2,564		)	(2,516		)
Amortization of actuarial gains	(172		)	(187		)	(447		)	(475		)
Net periodic benefit credit	$	(852	)	$	(721	)	$	(2,412	)	$	(2,066	)