Share-Based Compensation - RSU and RSA activity (Details) - USD ($) $ in Millions		12 Months Ended
	Sep. 25, 2015	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
RSUs
RSU and RSA activity ( including Performance RSUs and RSAs)
Outstanding at beginning of year		3,069,403
Granted (in shares)	987,496	3,959,496
Released (in shares)		(1,307,842)
Forfeited (in shares)		(781,283)
Outstanding at end of year		4,939,774	3,069,403
Additional disclosures
Aggregate intrinsic value outstanding		$ 127.9
Total estimated fair value of RSUs vested		32.4	$ 31.6	$ 25.1
Restricted shares
Additional disclosures
Aggregate intrinsic value outstanding		$ 20.1
Performance-Contingent Awards - RSAs
RSU and RSA activity ( including Performance RSUs and RSAs)
Outstanding at beginning of year		978,750
Granted (in shares)		0
Released (in shares)		0
Forfeited (in shares)		(202,500)
Outstanding at end of year		776,250	978,750