Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Income Taxes [Line Items]
Effective Income Tax Rate Reconciliation, Percent	21.6202%	21.50%
Total gross liability for unrecognized tax benefits	$ 37.8		$ 71.1
Significant Change in Unrecognized Tax Benefits, Nature of Event	33.3