Income Taxes - Carryforwards (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Carryforwards
Valuation allowance against deferred tax assets	$ 45.7	$ 40.5
UK
Carryforwards
Valuation allowance against deferred tax assets	10.0
UK | Capital loss carryforwards
Carryforwards
Tax credit carryforwards	2.6
Germany
Carryforwards
Net operating loss carryforwards	42.5
Valuation allowance against net operating loss carryforwards	16.8
Australia
Carryforwards
Net operating loss carryforwards	4.6
New Zealand
Carryforwards
Net operating loss carryforwards	4.8
Italy
Carryforwards
Net operating loss carryforwards	0.1
State | U.S.
Carryforwards
Net operating loss carryforwards	598.0
Net operating loss carryforwards utilized	5.3
Valuation allowance against net operating loss carryforwards	0.7
Valuation allowance against tax credit carryforwards	0.4
Federal and state | U.S.
Carryforwards
Tax credit carryforwards	4.1
Foreign | U.S.
Carryforwards
Tax credit carryforwards	20.1
Valuation allowance against tax credit carryforwards	$ 17.9