PENSION PLANS AND RETIREMENT BENEFITS (Tables)

3 Months Ended

Mar. 31, 2018

Retirement Benefits [Abstract]

Components of Net Periodic Benefit (Income) Cost

	Pension Benefits						Other Postretirement Benefits
	Three Months Ended March 31,						Three Months Ended March 31,
	2018			2017			2018		2017
Components of Net Periodic Benefit (Income) Cost	($ in millions)
Service cost	$	2.7		$	2.4		$	0.3	$	0.3
Interest cost	21.6			21.7			0.4		0.4
Expected return on plans’ assets	(36.8		)	(37.2		)	—		—
Amortization of prior service cost	—			—			—		(0.6		)
Recognized actuarial loss	8.8			6.6			0.6		0.6
Net periodic benefit (income) cost	$	(3.7	)	$	(6.5	)	$	1.3	$	0.7