Components of Net Periodic Benefit Cost for Pension and Postretirement Benefits (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended								6 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Pension Benefits	Dec. 31, 2012 Pension Benefits	Dec. 31, 2013 Pension Benefits Net Periodic Benefit Cost	Dec. 31, 2012 Pension Benefits Net Periodic Benefit Cost	Dec. 31, 2011 Pension Benefits Net Periodic Benefit Cost	Jun. 30, 2013 Postretirement Benefits	Dec. 31, 2013 Postretirement Benefits	Dec. 31, 2012 Postretirement Benefits	Dec. 31, 2013 Postretirement Benefits Net Periodic Benefit Cost	Dec. 31, 2012 Postretirement Benefits Net Periodic Benefit Cost	Dec. 31, 2011 Postretirement Benefits Net Periodic Benefit Cost
Defined Benefit Plan Disclosure [Line Items]
Service cost				$ 11.4	$ 12.1	$ 11.4	$ 12.1	$ 12.9		$ 0.3	$ 0.5	$ 0.3	$ 0.5	$ 0.5
Interest cost				30.1	30.7	30.1	30.7	31.0		1.7	3.9	1.7	3.9	4.4
Expected return on plan assets						(41.8)	(36.8)	(41.3)
Recognition of actuarial losses	5.2	42.2	80.0	(73.0)	66.0	0.8	30.6	80.0	4.0	(0.3)	9.9	4.4	11.6
Amortization of prior service cost (credits)				0.1		0.1	0.3	0.3		(19.4)		(27.4)	(2.6)	0.4
Curtailment and settlement losses						0.1		1.8				0.1
Net periodic benefit cost						$ 0.7	$ 36.9	$ 84.7				$ (20.9)	$ 13.4	$ 5.3