Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (7.8)	$ (5.5)	$ (41.8)	$ (32.4)
Other comprehensive income (loss), net of tax:
Foreign currency translation gain (loss)	2.8	1.5	(4.1)	3.1
Cash flow hedges:
Unrealized loss on cash flow hedges arising during the period, net of tax of ($0.2), $(2.3), ($3.2), ($3.3)	(0.7)	(7.8)	(10.8)	(10.9)
Reclassification adjustment for net losses included in net income, net of tax of $0.6, $0.0, $0.9, $0.1	1.7	0.2	2.8	0.4
Defined benefit plans:
Net (loss) gain arising from remeasurement during the period, net of tax of ($4.4), $0.0, ($4.4), $0.0	(14.7)	0.1	(14.7)	0.1
Amortization of prior service benefits included in net income, net of tax of ($0.2), ($0.2), ($0.3), ($0.3)	(0.5)	(0.5)	(1.0)	(1.0)
Amortization of net actuarial loss included in net income, net of tax of $1.2, $0.9, $2.2, $1.7	3.7	3.0	7.4	6.0
Reclassification adjustment for pension settlement charges included in net income, net of tax of $0.2, $0.2	0.9	0.0	0.9	0.0
Total other comprehensive loss	(6.8)	(3.5)	(19.5)	(2.3)
Total comprehensive loss	$ (14.6)	$ (9.0)	$ (61.3)	$ (34.7)