Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Unrecognized tax benefits	$ 0.0	$ 0.0
Interest expense in the consolidated income statements	0.0	0.0
Interest income in the consolidated income statements			$ 0.7
Penalties in the consolidated income statements	0.0	0.0	$ 0.0
Accrued interest on the consolidated balance sheets	0.0	0.0
Accrued penalties on the consolidated balance sheets	$ 0.0	$ 0.0