Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Income Taxes [Line Items]
Effective Income Tax Rate Reconciliation, Percent	24.33543%	21.50%
Total gross liability for unrecognized tax benefits	$ 36.8		$ 71.1
Significant Change in Unrecognized Tax Benefits, Nature of Event	34.3