Pension and Postretirement Benefits - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended			12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017		Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash contributions, pension plans	$ 27.4	$ 28.9		$ 138.4
Cash contributions, other postretirement benefits	30.9	31.7	[1]
Pension Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated cash contributions by the company	150.6
Pension Plans | U.S. Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated cash contributions by the company	86.3
Pension Plans | Non-U.S. Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated cash contributions by the company	64.3
Other Postretirement Benefit Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Estimated cash contributions by the company	12.0			$ 12.2
Cash contributions, other postretirement benefits	$ 3.5	$ 2.8

[1] *Amounts were changed to conform to the current-year presentation. See Note 3.