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Asset Retirement Obligations - Pledged Assets and Payables to ZionSolutions (Details) - USD ($) | Dec. 31, 2018 | Jun. 30, 2018 | Dec. 31, 2017
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Asset Retirement Obligations [Line Items] |  |  |  |
Line of credit facility, maximum borrowing capacity | [1] | $ 9,704,000,000 |  |
Asset retirement obligations, noncurrent |  | 9,679,000,000 |  | $ 10,029,000,000
Exelon Generation Co L L C [Member] |  |  |  |
Asset Retirement Obligations [Line Items] |  |  |  |
Line of credit facility, maximum borrowing capacity |  | 200,000,000 | $ 45,000,000 |
Asset retirement obligations, noncurrent |  | 9,450,000,000 |  | 9,844,000,000
Exelon Generation Co L L C [Member] | Nuclear Decommissioning Asset Retirement Obligation [Member] |  |  |  |
Asset Retirement Obligations [Line Items] |  |  |  |
Held-to-maturity Securities Pledged as Collateral | [2] | 9,000,000 |  | 39,000,000
Accounts Payable, Interest-bearing, Noncurrent |  | 9,000,000 |  | 37,000,000
Accounts Payable, Interest-bearing, Current |  | $ 965 |  | $ 942,000,000
[1] | Excludes $135 million of credit facility agreements arranged at minority and community banks at Generation, ComEd, PECO, BGE, Pepco, DPL and ACE with aggregate commitments of $49 million, $33 million, $34 million, $5 million, $5 million, $5 million and $5 million, respectively. These facilities expire on October 11, 2019. These facilities are solely utilized to issue letters of credit. As of December 31, 2018, letters of credit issued under these facilities totaled $5 million and $2 million for Generation and BGE, respectively.
[2] | (a)Included in Other current liabilities within Exelon's and Generation's Consolidated Balance Sheets. Excludes a liability recorded within Exelon’s and Generation’s Consolidated Balance Sheets related to the tax obligation on the unrealized gains and losses associated with the Zion Station NDT funds. The NDT funds will be utilized to satisfy the tax obligations as gains and losses are realized.

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- Definition Carrying value as of the balance sheet date of obligations incurred and payable to vendors that bear interest at either a stated or an imputed rate. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). + References 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 210.5-02.19(a)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28567-108399 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28541-108399 + Details
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- Definition Noncurrent portion of the carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + Details
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