Fair Value Measurement - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Assets
Total assets	$ 330.4	$ 2.2
Liabilities
Total liabilities	1.5	1.5
Foreign Exchange Forward Contracts
Assets
Total assets	1.7	1.8
Liabilities
Total liabilities	1.5	1.5
Interest Rate Swap
Assets
Total assets		0.4
Available-for-Sale Securities
Assets
Total assets	328.7
Significant other observable inputs (Level 2)
Assets
Total assets	330.4	2.2
Liabilities
Total liabilities	1.5	1.5
Significant other observable inputs (Level 2) | Foreign Exchange Forward Contracts
Assets
Total assets	1.7	1.8
Liabilities
Total liabilities	1.5	1.5
Significant other observable inputs (Level 2) | Interest Rate Swap
Assets
Total assets		$ 0.4
Significant other observable inputs (Level 2) | Available-for-Sale Securities
Assets
Total assets	$ 328.7