Income Taxes - Tax credit carryforwards (Details) $ in Thousands	Sep. 30, 2019 USD ($)
U.S. \| Foreign Tax Credits
Income tax credit carryforwards
Income tax credit carryforward	$ 14,535
U.S. \| Research and Development Tax Credits
Income tax credit carryforwards
Income tax credit carryforward	14,439
State \| Research and Development Tax Credits
Income tax credit carryforwards
Income tax credit carryforward	$ 25,748

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32559-109319

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