Earnings (Loss) per Share - Earnings per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share Reconciliation
Net income attributable to the Company	$ 41.6	$ 33.8	$ 32.1	$ 19.0	$ 9.1	$ (7.2)	$ 24.1	$ 9.2	$ 126.5	$ 35.2	$ 79.7
Basic and Diluted earnings (loss) per share
Basic earnings per share (usd per share)	$ 0.98	$ 0.80	$ 0.76	$ 0.45	$ 0.22	$ (0.17)	$ 0.57	$ 0.22	$ 3.00	$ 0.83	$ 1.89
Diluted earnings per share (usd per share)	$ 0.97	$ 0.79	$ 0.76	$ 0.45	$ 0.22	$ (0.17)	$ 0.57	$ 0.22	$ 2.97	$ 0.83	$ 1.89
Weighted average shares outstanding
Weighted average number of shares outstanding - Basic (shares)	42,100	42,100	42,100	42,100	42,100	42,100	42,100	42,100	42,130	42,108	42,102
Weighted average additional shares assuming conversion of potential common shares (shares)									399	163	0
Weighted average number of shares outstanding - Diluted (shares)	42,600	42,500	42,400	42,400	42,300	42,100	42,100	42,100	42,529	42,271	42,102