CONDENSED CONSOLIDATED BALANCE SHEETS CONDENSED CONSOLIDATED BALANCE SHEETS (Parentheticals) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Allowance for trade receivables	$ 0.3	$ 0.3
Accumulated depreciation	$ 204.4	$ 202.2
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	2,000,000,000	2,000,000,000	2,000,000,000
Common stock, shares issued (in shares)	146,296,962	146,085,696
Common stock, outstanding (in shares)	146,190,054	145,981,684
Treasury stock, at cost (in shares)	106,908	104,012