Share-Based Compensation - Stock Options (Details) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($) $ / shares shares
Options outstanding and exercisable under the Company's 1991 Equity and Performance Incentive Plan and 2017 Equity and Performance Incentive Plan
Outstanding at January 1, 2020 | shares	2.4
Outstanding at January 1, 2020 | $ / shares	$ 14.89
Expired or forfeited | shares	0.1
Expired or forfeited | $ / shares	$ 31.25
Granted | shares	0.4
Granted | $ / shares	$ 12.54
Outstanding at March 31, 2020 | shares	2.7
Outstanding at March 31, 2020 | $ / shares	$ 14.38
Outstanding, weighted-average remaining contractual term	8 years
Outstanding, aggregate intrinsic value | $	$ 7.0
Options exercisable at March 31, 2020 | shares	1.4
Options exercisable at March 31, 2020 | $ / shares	$ 19.82
Options exercisable, weighted-average remaining contractual term	7 years
Options exercisable, aggregate intrinsic value | $	$ 2.3
Options vested and expected to vest(2) at March 31, 2020 | shares	2.7
Options vested and expected to vest(2) at March 31, 2020 | $ / shares	$ 14.38
Options vested and expected to vest, weighted-average remaining contractual term	8 years
Options vested and expected to vest, aggregate intrinsic value | $	$ 7.0