Significant Accounting Policies (Inventories) (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Net change in inventory reserves	$ (0.2)	$ 0.4	$ 0.7
Amortization included in cost of products sold	$ 2.3	$ 2.3	$ 2.1

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