Leases - Schedule of Balance Sheet Presentation of Operating and Finance Leases (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jul. 01, 2019
Assets:
Operating leases, right-of-use asset, net	$ 851	$ 414	$ 1,600
Financing lease assets	$ 52
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:PropertyPlantAndEquipmentNet
Total lease assets	$ 903
Liabilities:
Operating lease obligations, Current	$ 330
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	astc:OperatingAndFinanceLeaseLiabilityCurrent
Financing lease obligations, Current	$ 9
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	astc:OperatingAndFinanceLeaseLiabilityCurrent
Operating lease obligations, Non-current	$ 583
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	astc:OperatingAndFinanceLeaseLiabilityNoncurrent
Financing lease obligations, Non-current	$ 40
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	astc:OperatingAndFinanceLeaseLiabilityNoncurrent
Total lease liabilities	$ 962