Accumulated Other Comprehensive Loss - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Amounts reclassified out of accumulated other comprehensive income related to defined benefit pension plans as component of net periodic benefit cost, actuarial net loss	$ 0.5	$ 0.5	$ 1.6	$ 1.4

Amount, before tax, of reclassification adjustment from accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan.

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