Net Loss Per Share and Shareholders' Equity - Reconciliation of Numerator and Denominator of the Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Net earnings (loss)	$ 14.9	$ 10.1	$ 20.8	$ (14.5)
Denominator:
Denominator for basic EPS–weighted-average common shares (in shares)	69,646,435	68,500,028	69,432,137	68,380,684
Dilutive effect of stock-based compensation arrangements (in shares)	2,057,285	2,438,490	2,193,326	0
Denominator for diluted EPS–adjusted weighted-average common shares (in shares)	71,703,720	70,938,518	71,625,463	68,380,684
Basic EPS (in dollars per share)	$ 0.21	$ 0.15	$ 0.30	$ (0.21)
Diluted EPS (in dollars per share)	$ 0.21	$ 0.14	$ 0.29	$ (0.21)