Earnings Per Share - Antidilutive Securities (Details) - shares shares in Thousands	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
Total anti-dilutive securities	5,730	4,060	5,450	5,110
Share-based awards
Antidilutive Securities Excluded from Computation of Earnings Per Share
Total anti-dilutive securities	260	690	270	1,740
Convertible note hedge
Antidilutive Securities Excluded from Computation of Earnings Per Share
Total anti-dilutive securities	290	0	0	0
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share
Total anti-dilutive securities	5,180	3,370	5,180	3,370