Inventories (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Inventory, Net [Abstract]
Separative work units inventory	$ 416.3	$ 628.4
Uranium inventory	89.3	335.4
Materials and supplies	1.2	3.8
Inventories	506.8	967.6
Separative work units owed to customers and suppliers	77.4	200.0
Uranium owed to customers and suppliers	89.2	299.7
Inventories owed to customers and suppliers	166.6	499.7
Separative work units net of liability	338.9	428.4
Uranium inventory net of liability	0.1	35.7
Inventories, net	$ 340.2	$ 467.9