Presentation of Financial Information - Earning Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Apr. 02, 2017	Apr. 03, 2016	Apr. 02, 2017	Apr. 03, 2016
BASIC
Net income (loss)	$ 41.2	$ (212.0)	$ 60.6	$ (188.3)
Weighted-average common shares outstanding (in shares)	114,700,000	109,600,000	114,400,000	102,000,000
Basic earnings (loss) per share (USD per share)	$ 0.36	$ (1.93)	$ 0.53	$ (1.85)
DILUTED
Net income (loss)	$ 41.2	$ (212.0)	$ 60.6	$ (188.3)
Weighted-average common shares outstanding (in shares)	114,700,000	109,600,000	114,400,000	102,000,000
Dilutive effect of stock awards	2,300,000	0	2,200,000	0
Weighted-average common shares outstanding on a diluted basis (in shares)	117,000,000	109,600,000	116,600,000	102,000,000
Diluted earnings per share (USD per share)	$ 0.35	$ (1.93)	$ 0.52	$ (1.85)
Stock awards excluded in computation of diluted EPS			0