Earnings (Loss) Per Share - Anti-dilutive Securities (Details) - shares shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted-average securities not included in computation of diluted shares outstanding (in shares)	5.2	15.3	5.6	15.9
Shares issuable upon conversion of PDH Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted-average securities not included in computation of diluted shares outstanding (in shares)	0.0	6.0	0.0	6.8
Shares issuable upon conversion of Series A Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted-average securities not included in computation of diluted shares outstanding (in shares)	0.0	2.0	0.0	2.0
Shares issuable for the contingent consideration
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted-average securities not included in computation of diluted shares outstanding (in shares)	4.4	6.3	5.0	6.2
Shares issuable upon vesting and exercise of stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted-average securities not included in computation of diluted shares outstanding (in shares)	0.0	0.1	0.0	0.1
Shares issuable upon vesting of RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted-average securities not included in computation of diluted shares outstanding (in shares)	0.8	0.9	0.6	0.8