Income Taxes - Tax credit carryforwards (Details) $ in Thousands	Sep. 30, 2017 USD ($)
U.S.
Income tax credit carryforwards
Income tax credit carryforward	$ 21,900
U.S. \| Foreign Tax Credits
Income tax credit carryforwards
Income tax credit carryforward	15,567
U.S. \| Research and Development Tax Credits
Income tax credit carryforwards
Income tax credit carryforward	6,303
State
Income tax credit carryforwards
Income tax credit carryforward	20,500
State \| Research and Development Tax Credits
Income tax credit carryforwards
Income tax credit carryforward	$ 20,486

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