Retirement Benefits

6 Months Ended

Jun. 30, 2015

Compensation and Retirement Disclosure [Abstract]

Retirement Benefits

Retirement Benefits

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

	Three Months Ended						Six Months Ended
	June 30, 2015			June 30, 2014			June 30, 2015			June 30, 2014
	(Dollars in thousands)
Service cost	$	3,951		$	3,316		$	8,001		$	6,771
Interest cost	7,142			7,419			14,291			14,849
Expected return on plan assets	(15,698		)	(14,333		)	(31,353		)	(28,688		)
Amortization of prior service cost	268			334			514			619
Amortization of actuarial losses	1,833			217			3,666			434
Net periodic benefit credit	$	(2,504	)	$	(3,047	)	$	(4,881	)	$	(6,015	)

The components of the net periodic other postretirement benefits costs were as follows:

	Three Months Ended						Six Months Ended
	June 30, 2015			June 30, 2014			June 30, 2015			June 30, 2014
	(Dollars in thousands)
Service cost	$	136		$	126		$	279		$	264
Interest cost	349			417			709			825
Amortization of prior service credit	(736		)	(714		)	(1,472		)	(1,428		)
Amortization of actuarial gains	(63		)	(86		)	(127		)	(171		)
Net periodic benefit credit	$	(314	)	$	(257	)	$	(611	)	$	(510	)