Earnings (Loss) Per Share - Computation of Weighted Average Shares Outstanding (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Schedule of Earnings Per Share [Line Items]
Net income (loss) attributable to common stockholders	$ 12.0	$ (61.1)	$ 49.3	$ (85.5)
Numerator adjustments for diluted EPS:
Income allocated to PDH non-controlling interest	(0.6)	0.0	0.6	0.0
Remeasurement of contingent consideration	0.0	0.0	0.1	0.0
Numerator adjustments for diluted EPS:	(0.6)	0.0	0.7	0.0
Net income (loss) attributable to common stockholders for diluted EPS	$ 11.4	$ (61.1)	$ 50.0	$ (85.5)
Basic weighted average common shares outstanding (in shares)	288.2	286.1	288.0	285.3
Denominator adjustments for diluted EPS:
Number of shares issuable upon conversion of founder preferred stock (in shares)	2.0	0.0	2.0	0.0
Number of shares contingently issuable for the contingent consideration (in shares)	3.0	0.0	3.0	0.0
Number of shares issuable upon conversion of the PDH non-controlling interest (in shares)	4.1	0.0	4.2	0.0
Number of stock options, RSUs and shares issued through employee stock purchase plan (in shares)	0.7	0.0	0.7	0.0
Denominator adjustments for diluted EPS (in shares)	9.8	0.0	9.9	0.0
Dilutive weighted average common shares outstanding (in shares)	298.0	286.1	297.9	285.3
Earnings (loss) per share attributable to common stockholders:
Basic (in dollars per share)	$ 0.04	$ (0.21)	$ 0.17	$ (0.30)
Diluted (in dollars per share)	0.04	(0.21)	0.17	(0.30)
Dividends per share paid to common stockholders (in dollars per share)	$ 0	$ 0	$ 0	$ 0