Income (Loss) Per Common Share - Shares Excluded from EPS (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Common share equivalents
Diluted income (loss) per share
Securities excluded from the diluted calculation as their effect would be antidilutive	320	169
Potentially dilutive shares
Diluted income (loss) per share
Securities excluded from the diluted calculation as their effect would be antidilutive	2,426	2,092
Potential shares to be issued for settlement of the Convertible Senior Notes
Diluted income (loss) per share
Securities excluded from the diluted calculation as their effect would be antidilutive	8,618	8,618