Fair Value Measurements - Schedule of Assets Measured at Fair Value on a Recurring Basis (Details) - Measured on Recurring Basis - USD ($) $ in Millions	Oct. 01, 2017	Jan. 01, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	$ 4.2	$ 4.0
Available-for-sale investment	212.4	141.2
Total assets at fair value	216.6	145.2
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	4.2	4.0
Available-for-sale investment	212.4	141.2
Total assets at fair value	216.6	145.2
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	0.0	0.0
Available-for-sale investment	0.0	0.0
Total assets at fair value	0.0	0.0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	0.0	0.0
Available-for-sale investment	0.0	0.0
Total assets at fair value	$ 0.0	$ 0.0