Inventories (Narrative) (Details) (USD $) In Billions, unless otherwise specified	9 Months Ended
Sep. 30, 2013	Dec. 31, 2012
Inventory, Net [Abstract]
Inventories provided by customers and suppliers	$ 1.5	$ 1.9
Decline in Uranium Spot Price Indicator	19.00%
Decline in Uranium Quantities Provided by Customers and Suppliers	5.00%

Uranium held by USEC to which title was held by customers and suppliers and for which no assets or liabilities were recorded on the balance sheet

No definition available.

Name:	usu_InventoriesProvidedByCustomersAndSuppliers
Namespace Prefix:	usu_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant