Benefit Plans - Pension Plans with Accumulated Benefit Obligation or Projected Benefit Obligation in Excess of Plan Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
U.S.
Pension plans with a projected benefit obligation in excess of plan assets:
Projected benefit obligation	$ 463.0	$ 87.2
Fair value of plan assets	374.5	17.5
Pension plans with an accumulated benefit obligation in excess of plan assets:
Projected benefit obligation	463.0	87.2
Fair value of plan assets	374.5	17.5
Accumulated benefit obligation	460.3	86.3
Foreign Plan [Member]
Pension plans with a projected benefit obligation in excess of plan assets:
Projected benefit obligation	182.4	165.2
Fair value of plan assets	22.6	20.9
Pension plans with an accumulated benefit obligation in excess of plan assets:
Projected benefit obligation	170.3	165.2
Fair value of plan assets	11.4	20.9
Accumulated benefit obligation	$ 160.5	$ 155.7