Inventory (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Inventory Disclosure [Abstract]
Cost of goods sold, amortization of operating materials	$ 0.6	$ 0.6

Cost of goods sold, amortization of operating materials.

No definition available.

Name:	usap_CostOfGoodsSoldAmortizationOfOperatingMaterials
Namespace Prefix:	usap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration