Retirement Plans (Tables)

3 Months Ended

Mar. 31, 2016

Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]

Net period benefit cost for the pension and postretirement plans

The components of net periodic benefit cost for the RAP and Postretirement Plans for three months ended March 31, 2016 and 2015 were as follows.

	Three Months Ended March 31,
	2016			2015
	($ in Thousands)
Components of Net Periodic Benefit Cost
Pension Plan:
Service cost	$	1,725		$	3,063
Interest cost	1,780			1,642
Expected return on plan assets	(5,065		)	(5,350		)
Amortization of prior service cost	13			13
Amortization of actuarial loss	482			532
Total net pension cost	$	(1,065	)	$	(100	)
Postretirement Plan:
Interest cost	$	36		$	35
Total net periodic benefit cost	$	36		$	35