Selected Quarterly Financial Data (unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 207.4	$ 197.8	$ 207.1	$ 207.2	$ 214.5	$ 230.1	$ 233.9	$ 249.7	$ 819.5	$ 928.2	$ 887.4
Operating income	83.8	51.9	46.6	68.0	29.6	13.3	15.3	25.6	250.3	83.8	71.0
Income from continuing operations before income taxes	88.6	51.0	35.7	82.7	34.9	10.7	6.1	83.5	258.0	135.2	142.0
Net income	74.3	83.0	21.6	61.1	18.8	54.2	2.5	54.8	$ 223.9	$ 136.4	$ 4.2
Net income attributable to controlling interests	$ 67.8	$ 75.4	$ 28.0	$ 52.7	$ 23.0	$ 54.0	$ 2.1	$ 57.3
Earnings per share (basic) attributable to controlling interests (in dollars per share)	$ 0.79	$ 0.84	$ 0.31	$ 0.54	$ 0.22	$ 0.51	$ 0.02	$ 0.52	$ 2.45	$ 1.27	$ 0.04
Earnings per share (diluted) attributable to controlling interests (in dollars per share)	$ 0.79	$ 0.84	$ 0.31	$ 0.54	$ 0.22	$ 0.51	$ 0.02	$ 0.52	$ 2.45	$ 1.26	$ 0.04
Weighted average shares outstanding (in shares)	85,900,000	90,000,000.0	91,500,000	97,600,000	105,600,000	106,400,000	108,400,000	109,400,000	91,205,412	107,431,821	110,708,598
Weighted average diluted shares outstanding (in shares)	85,900,000	90,000,000.0	91,500,000	97,800,000	105,800,000	106,500,000	108,600,000	109,600,000	91,268,952	107,623,192	111,381,142