Net Loss Per Common Share Schedule of Antidilutive Securities (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	7.2	4.5	7.2	4.5
Options outstanding to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	0.4	0.8	0.4	0.8
Unvested restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	2.8	3.7	2.8	3.7
Senior convertible notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	4.0	0.0	4.0	0.0