Income Taxes - Carryforwards (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Operating Loss Carryforwards
Foreign pre-tax loss	$ 0.0	$ 3.0
Federal
Operating Loss Carryforwards
Net operating loss carryforwards	638.9
Net operating loss carryforwards with no expiration date	146.0
Federal | R&D credit
Operating Loss Carryforwards
Tax credit carryforwards	33.4
State
Operating Loss Carryforwards
Net operating loss carryforwards	595.1
State | R&D credit
Operating Loss Carryforwards
Tax credit carryforwards	11.7
Australian Subsidiary
Operating Loss Carryforwards
Foreign Net Operating Loss written off	$ 14.9