Income Taxes - NOL and Tax credit carryforwards (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
State
NOL and Tax credit carryfowards
Net operating loss carryforwards	$ 192.0	$ 117.2
Foreign
NOL and Tax credit carryfowards
Tax credit carryforwards	72.8	$ 46.0
Federal
NOL and Tax credit carryfowards
Net operating loss carryforwards	$ 26.4

The amount of the tax credit carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32559-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Carryforwards
-URI http://asc.fasb.org/extlink&oid=6506874

Name:	us-gaap_TaxCreditCarryforwardAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant