Segment Information (Segment Reporting Information) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenue:
Separative work units									$ 1,821.8	$ 1,330.9	$ 1,521.4
Uranium									26.0	131.8	236.1
Revenue from low enriched uranium segment									1,847.8	1,462.7	1,757.5
Contract services revenue									70.3	209.1	277.9
Total revenue	421.3	570.5	364.8	561.5	462.4	374.5	454.4	380.5	1,918.1	1,671.8	2,035.4
LEU segment gross profit									129.3	71.6	134.3
Contract services segment gross profit									8.7	12.6	24.1
Gross profit									138.0	84.2	158.4
One-time termination benefits									3.9
Advanced technology costs	1,146.4	45.1	85.7	36.8	187.0	26.0	33.5	26.7	1,314.0	273.2	110.2
Selling, general and administrative	13.6	12.8	14.8	14.9	14.3	15.6	16.7	15.5	56.1	62.1	58.9
Other (income)	$ (47.5)	$ (34.6)	$ (10.0)					$ (3.7)	$ (92.1)	$ (3.7)	$ (44.4)

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