Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Nov. 30, 2015
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ 7.0	$ (9.2)	$ 18.0	$ (16.2)
Other comprehensive income (loss):
Amortization of net actuarial losses, net of $24.5 million, $23.2 million, $31.3 million, and $1.7 million of income taxes in fiscal 2017, 2016, 2015, and one month ended December 31, 2015, respectively	3.4	39.0	37.1	49.4
Actuarial (losses) gains, net of $2.9 million, $4.8 million, $36.9 million, and $4.6 million of income taxes in fiscal 2017, 2016, 2015, and one month ended December 31, 2015, respectively	(8.6)	(8.5)	7.5	(56.6)
Amortization of prior service credits, net of $0.0 million, $0.4 million, $0.4 million, and $0.0 million of income taxes in fiscal 2017, 2016, 2015, and one month ended December 31, 2015, respectively	(0.1)	(0.1)	(0.6)	(0.8)
Other comprehensive income (loss), net of income taxes	(5.3)	30.4	44.0	(8.0)
Comprehensive income (loss)	$ 1.7	$ 21.2	$ 62.0	$ (24.2)