Significant Accounting Policies (Inventories) (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Net change in inventory reserves	$ 0.4	$ 0.7	$ 0.5
Amortization included in cost of products sold	$ 2.3	$ 2.1	$ 1.6

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