Benefit Plans (Tables)

6 Months Ended

Jun. 30, 2016

Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]

Schedule of Components of Net Periodic Benefit Cost

The components of net periodic benefit cost for the three months ended June 30 were as follows ($ in millions):

	Pension benefits						Other retirement benefits						Total
	2016			2015			2016			2015			2016			2015
Service cost	$	2.7		$	2.7		$	0.1		$	0.2		$	2.8		$	2.9
Interest cost	2.6			3.9			0.1			0.1			2.7			4.0
Expected return on assets	(3.2		)	(5.7		)	—			—			(3.2		)	(5.7		)
Amortization of prior service credit	(0.3		)	(0.3		)	—			—			(0.3		)	(0.3		)
Recognized actuarial losses (gains)	1.1			1.6			(0.3		)	(0.4		)	0.8			1.2
Net periodic benefit cost	$	2.9		$	2.2		$	(0.1	)	$	(0.1	)	$	2.8		$	2.1

	Pension benefits				Other retirement benefits						Total
	2016		2015		2016			2015			2016		2015
U.S. plans	$	2.3	$	1.6	$	(0.1	)	$	(0.1	)	$	2.2	$	1.5
International plans	0.6		0.6		—			—			0.6		0.6
Net periodic benefit cost	$	2.9	$	2.2	$	(0.1	)	$	(0.1	)	$	2.8	$	2.1

The components of net periodic benefit cost for the six months ended June 30 were as follows ($ in millions):

	Pension benefits						Other retirement benefits						Total
	2016			2015			2016			2015			2016			2015
Service cost	$	5.3		$	5.4		$	0.3		$	0.3		$	5.6		$	5.7
Interest cost	5.2			7.8			0.2			0.2			5.4			8.0
Expected return on assets	(6.3		)	(11.4		)	—			—			(6.3		)	(11.4		)
Amortization of prior service credit	(0.7		)	(0.6		)	—			—			(0.7		)	(0.6		)
Recognized actuarial losses (gains)	2.3			3.2			(0.7		)	(0.7		)	1.6			2.5
Net periodic benefit cost	$	5.8		$	4.4		$	(0.2	)	$	(0.2	)	$	5.6		$	4.2

	Pension benefits				Other retirement benefits						Total
	2016		2015		2016			2015			2016		2015
U.S. plans	$	4.6	$	3.1	$	(0.2	)	$	(0.2	)	$	4.4	$	2.9
International plans	1.2		1.3		—			—			1.2		1.3
Net periodic benefit cost	$	5.8	$	4.4	$	(0.2	)	$	(0.2	)	$	5.6	$	4.2