Accounting Policies (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Retained Earnings Adjustments [Line Items]
Impact of change in accounting policy		$ 0
Operating leases (less than)	$ 2,200
Accounting Standards Update 2014-09
Retained Earnings Adjustments [Line Items]
Impact of change in accounting policy		$ (102)

Contractually required future rental payments receivable on noncancelable subleasing arrangements.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41502-112717

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