Accounts Receivable (Table) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Accounts Receivable
Utility Customer Receivables	$ 106.1	$ 118.3
Receivable on Sale of NAC subsidiary	3.3
DOE pro-rata share of RD&D program funding	33.0	4.4
Contract Services Billed Revenue	8.7	10.5
Contract Services Unbilled Revenue	2.1	1.6
Contract Services Customer Receivables	10.8	12.1
Accounts Receivable, Net	$ 153.2	$ 134.8

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 210.5-02.3-4)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 3

-Subparagraph a(1)

-Article 5

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 4

-Article 5

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Balance Type:	debit
Period Type:	instant