Income Taxes - Schedule Of Deferred Tax Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Share-based compensation expense	$ 122.2	$ 140.5
Expenses deducted in later years for tax purposes	47.4	47.1
Research and other credits	15.6	13.5
Other	9.8	7.5
Gross deferred tax assets	195.0	208.6
Valuation allowance	(17.2)	(15.2)
Deferred tax assets	177.8	193.4
Deferred tax liabilities:
Fixed assets	(25.2)	(24.0)
Intangible assets	(2.3)	(2.0)
Other	(0.2)	(0.5)
Deferred tax liabilities	(27.7)	(26.5)
Net deferred tax assets	$ 150.1	$ 166.9