2.2.0.7 false Intangible Assets (Details) (USD $) 4050 - Disclosure - Intangible Assets (Details) true false In Millions false false 1 USD false false USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 USDPerShare Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 $ false 2 USD false false USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USDPerShare Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 $ 3 Changes in goodwill 1 us-gaap_GoodwillRollForward us-gaap true na duration No definition available. false false false false false true false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. false 4 Gross goodwill, beginning balance 2 ceg_GoodwillGross ceg false debit instant Gross amount, as of the balance sheet date, of the cumulative amount paid and (if applicable) the fair value of any... false false false false false false false false true false false periodstartlabel false 1 true true false false 271100000 271.1 false false false 2 true true false false 261300000 261.3 false false false xbrli:monetaryItemType monetary Gross amount, as of the balance sheet date, of the cumulative amount paid and (if applicable) the fair value of any noncontrolling interest in the acquiree, adjusted for any amortization recognized prior to the adoption of any changes in generally accepted accounting principles (as applicable), in excess of the fair value of net assets acquired in one or more business combination transactions. No authoritative reference available. false 5 Accumulated impairment losses, beginning balance 2 ceg_GoodwillImpairedAccumulatedImpairmentLoss ceg false credit instant The accumulated impairment losses related to goodwill as of the balance sheet date. false false false false false false false false true false false periodstartlabel false 1 false true false false -266500000 -266.5 false false false 2 false false false false 0 0 false false false xbrli:monetaryItemType monetary The accumulated impairment losses related to goodwill as of the balance sheet date. No authoritative reference available. false 6 Net goodwill, beginning balance 2 us-gaap_Goodwill us-gaap true debit instant No definition available. false false false false false false false false true false false periodstartlabel false 1 false true false false 4600000 4.6 false false false 2 false true false false 261300000 261.3 false false false xbrli:monetaryItemType monetary Carrying amount as of the balance sheet date, which is the cumulative amount paid, adjusted for any amortization recognized prior to adoption of FAS 142 and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 142 -Paragraph 43 false 7 Goodwill acquired 2 us-gaap_GoodwillAcquiredDuringPeriod us-gaap true debit duration No definition available. false false false false false false false false false false false terselabel false 1 false true false false 18600000 18.6 false false false 2 false true false false 9800000 9.8 false false false xbrli:monetaryItemType monetary The aggregate amount of goodwill acquired in the period and allocated to the reportable segment. The value is stated at fair value based on the purchase price allocation. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 142 -Paragraph 45 -Subparagraph e(1) false 8 Goodwill impairment 2 us-gaap_GoodwillImpairmentLoss us-gaap true debit duration No definition available. false false false false false false false false false false false terselabel false 1 false false false false 0 0 false false false 2 false true false false -266500000 -266.5 false false false xbrli:monetaryItemType monetary Loss recognized during the period that results from the write-down of goodwill after comparing the implied fair value of reporting unit goodwill with the carrying amount of that goodwill. Goodwill is assessed at least annually for impairment. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 142 -Paragraph 45 -Subparagraph e(2) Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 142 -Paragraph 43 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 142 -Paragraph 47 -Subparagraph b Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 142 -Paragraph 20 false 9 Other purchase price adjustments 2 ceg_GoodwillPurchaseAccountingAdjustments ceg false debit duration Purchase accounting adjustments needed to revise the carrying amount of goodwill to fair value. false false false false false false false false false false false terselabel false 1 false true false false 2300000 2.3 false false false 2 false false false false 0 0 false false false xbrli:monetaryItemType monetary Purchase accounting adjustments needed to revise the carrying amount of goodwill to fair value. No authoritative reference available. false 10 Gross goodwill, ending balance 2 ceg_GoodwillGross ceg false debit instant Gross amount, as of the balance sheet date, of the cumulative amount paid and (if applicable) the fair value of any... false false false false false false false false false true false periodendlabel false 1 false true false false 292000000 292.0 false false false 2 false true false false 271100000 271.1 false false false xbrli:monetaryItemType monetary Gross amount, as of the balance sheet date, of the cumulative amount paid and (if applicable) the fair value of any noncontrolling interest in the acquiree, adjusted for any amortization recognized prior to the adoption of any changes in generally accepted accounting principles (as applicable), in excess of the fair value of net assets acquired in one or more business combination transactions. No authoritative reference available. false 11 Accumulated impairment losses, ending balance 2 ceg_GoodwillImpairedAccumulatedImpairmentLoss ceg false credit instant The accumulated impairment losses related to goodwill as of the balance sheet date. false false false false false false false false false true false periodendlabel false 1 false true false false -266500000 -266.5 false false false 2 false true false false -266500000 -266.5 false false false xbrli:monetaryItemType monetary The accumulated impairment losses related to goodwill as of the balance sheet date. No authoritative reference available. false 12 Net goodwill, ending balance 2 us-gaap_Goodwill us-gaap true debit instant No definition available. false false false false false false false false false true false periodendlabel false 1 false true false false 25500000 25.5 false false false 2 false true false false 4600000 4.6 false false false xbrli:monetaryItemType monetary Carrying amount as of the balance sheet date, which is the cumulative amount paid, adjusted for any amortization recognized prior to adoption of FAS 142 and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 142 -Paragraph 43 false 13 Goodwill balance deductible for tax purposes 1 us-gaap_BusinessAcquisitionPurchasePriceAllocationGoodwillExpectedTaxDeductibleAmount us-gaap true debit instant No definition available. false false false false false false false false false false false terselabel false 1 true true false false 18600000 18.6 false false false 2 false false false false 0 0 false false false xbrli:monetaryItemType monetary The amount of goodwill arising from a business combination that is expected to be deductible for tax purposes. 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