Revenue Recognition and Contracts with Customers (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Advances from customers, noncurrent	$ 14.5		$ 0.0
Deferred revenue, revenue recognized	20.2
Accounts receivable, net	2.5	$ 60.3	60.2
Government [Member]
Litigation Settlement, Amount Awarded from Other Party	24.0
Accounts receivable, net			14.5
Proceeds from Customers	4.7
Advances from customers			19.3
Gain (Loss) Related to Litigation Settlement	9.5
Low Enriched Uranium Segment [Member]
Revenue, Remaining Performance Obligation	$ 1,100.0		$ 1,300.0

Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3))
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The current portion of prepayments received from customers for goods or services to be provided in the future.

+ References

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The noncurrent portion of deferred revenue amount as of balance sheet date. Deferred revenue is a liability related to a revenue producing activity for which revenue has not yet been recognized, and is not expected to be recognized in the next twelve months. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Amount of revenue recognized that was previously reported as deferred or unearned revenue.

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Amount of gain (loss) recognized in settlement of litigation and insurance claims. Excludes claims within an insurance entity's normal claims settlement process.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Amount awarded from other party in judgment or settlement of litigation.

+ References

No definition available.

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- Definition

Cash receipts from customers during the current period which are usually for sales of goods and services.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Amount of transaction price allocated to performance obligation that has not been recognized as revenue.

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