Employee Benefit Plans (Tables)

6 Months Ended

Jun. 30, 2018

Compensation And Retirement Disclosure [Abstract]

Schedule of components of period benefit costs

The components of periodic benefit costs for the three and six months ended June 30, 2018 and June 30, 2017 are as follows:

	Three Months Ended June 30, 2018									Six Months Ended June 30, 2018
							Postretirement									Postretirement
	U.S.			Non-U.S.			Health and			U.S.			Non-U.S.			Health and
	Pension			Pension			Other			Pension			Pension			Other
($ in millions)	Plans			Plans			Plans			Plans			Plans			Plans
Service cost - benefits earned during the period	$	—		$	0.5		$	0.1		$	—		$	1.0		$	0.2
Interest cost of projected benefit obligations		1.3			0.5			0.2			2.6			1.0			0.4
Expected return on plan assets		(1.5	)		(0.4	)		—			(3.0	)		(0.8	)		—
Amortization of prior service cost		—			—			(0.7	)		—			—			(1.4	)
Amortization of actuarial net loss		0.8			0.4			0.2			1.6			0.8			0.4
Net periodic benefit costs	$	0.6		$	1.0		$	(0.2	)	$	1.2		$	2.0		$	(0.4	)

	Three Months Ended June 30, 2017									Six Months Ended June 30, 2017
							Postretirement									Postretirement
	U.S.			Non-U.S.			Health and			U.S.			Non-U.S.			Health and
	Pension			Pension			Other			Pension			Pension			Other
($ in millions)	Plans			Plans			Plans			Plans			Plans			Plans
Service cost - benefits earned during the period	$	—		$	0.5		$	—		$	—		$	0.9		$	0.1
Interest cost of projected benefit obligations		1.4			0.4			0.3			2.7			1.0			0.5
Expected return on plan assets		(1.3	)		(0.3	)		—			(2.5	)		(0.7	)		—
Amortization of prior service cost		—			—			(0.4	)		—			—			(0.7	)
Amortization of actuarial net loss		0.8			0.4			0.1			1.6			0.8			0.2
Net periodic benefit costs		0.9			1.0			0.0			1.8			2.0			0.1