Recent Accounting Pronouncements Not Yet Adopted - Additional Information (Detail) - Defined Benefit Pension Plans - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2.8	$ 2.5	$ 5.5	$ 5.0	$ 9.9
Net periodic defined benefit pension costs	$ 7.3	$ 5.9	$ 14.3	$ 11.7	$ 22.9