Investments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jul. 01, 2017	Jul. 02, 2016	Jul. 01, 2017	Jul. 02, 2016	Dec. 31, 2016
Unrealized Gain (Loss) on Investments [Abstract]
Gross unrealized losses	$ 1.9		$ 1.9		$ 0.0
Impairment of investments					1.7
Gain on sale of investments			1.6
Gains (loss) from equity method investments	0.2	$ (1.6)	0.3	$ (3.9)
Equity method investment, other than temporary impairment			22.3
Transfer from investments		15.5
Unrealized gain (loss) on investments		$ 8.7
Estimated fair value of equity securities
Unrealized Gain (Loss) on Investments [Abstract]
Equity securities, at cost less impairments	15.5		15.5		16.5
Gross unrealized gains					21.7
Gross unrealized losses	0.0		0.0
Estimated fair value of equity securities	13.6		13.6		38.2
Other non-current assets
Unrealized Gain (Loss) on Investments [Abstract]
Cost method investments	7.1		7.1		6.9
Equity method investments	$ 4.9		$ 4.9		$ 4.6