Earnings Per Share And Shareholder's Equity - Earnings Per Share (Details) - USD ($) shares in Millions, $ in Millions		3 Months Ended													12 Months Ended
		Dec. 31, 2018	Sep. 29, 2018	[1]	Jun. 30, 2018	[2]	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	[3]	Jul. 01, 2017	[4]	Apr. 01, 2017	[5]	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator:
Net income		$ 81.5	$ (67.5)		$ 36.2		$ 80.8	$ 73.1	$ 44.5		$ (69.6)		$ 71.6		$ 131.0	$ 119.6	$ (4,012.8)
Denominator:
Basic (in shares)		135.9	137.4		138.1		140.8	140.8	141.3		143.3		143.4		137.8	142.3	143.3
Dilutive effect of share-based awards	[6]														0.5	0.3	0.0
Diluted (in shares)		136.3	137.4		138.7		141.4	141.2	141.7		143.3		143.6		138.3	142.6	143.3
Antidilutive share-based awards oustanding	[6]														1.4	0.8	0.0

[1] Includes of $221.8 million and of $18.0 million

[2] Includes of $53.2 million.

[3] Includes of $3.3 million, and of $4.0 million.

[4] Includes of $18.5 million, and of $135.2 million.

[5] Includes of $12.2 million, of $21.8 million, and restructuring expense of $38.7 million.

[6] In the period of a net loss, diluted shares equal basic shares.