Summary Of Pre Tax Amounts Recognized In Other Comprehensive Income (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Pension And Other Retirement Benefits Recognized In Accumulated Other Comprehensive Income Loss [Line Items]
Amortization of prior service costs	$ 13.5	$ 7.3	$ 11.9
Net actuarial gain (loss) arising during period	18.5	(93.8)	$ 50.9
Pension Plans [Member]
Schedule Of Pension And Other Retirement Benefits Recognized In Accumulated Other Comprehensive Income Loss [Line Items]
Amortization of net acturial losses	12.5	6.6
Amortization of prior service costs	0.7	0.7
Prior service costs	6.5
Net actuarial gain (loss) arising during period	8.4	(87.5)
Total recognized in OCI - pre-tax	28.1	(80.2)
Other Retirement Plans [Member]
Schedule Of Pension And Other Retirement Benefits Recognized In Accumulated Other Comprehensive Income Loss [Line Items]
Amortization of net acturial losses	0.3
Prior service costs	1.2
Net actuarial gain (loss) arising during period	1.3	(3.7)
Total recognized in OCI - pre-tax	$ 2.8	$ (3.7)