Fair Value Measurements - Fair Value Measurements on a Recurring Basis (Details) - USD ($) $ in Millions	Jan. 03, 2016	Dec. 28, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment	$ 142.3	$ 97.9
Measured on a recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	3.7	3.3
Available-for-sale investment	142.3	97.9
Total assets at fair value	146.0	101.2
Measured on a recurring basis | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	3.7	3.3
Available-for-sale investment	142.3	97.9
Total assets at fair value	146.0	101.2
Measured on a recurring basis | 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
Measured on a recurring basis | 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