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Property Plant and Equipment | 12 Months Ended
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Dec. 31, 2017
Property, Plant and Equipment [Abstract] |
PROPERTY, PLANT AND EQUIPMENT | PROPERTY, PLANT AND EQUIPMENT The following table summarizes the components of the electric generation and distribution assets and other property, plant and equipment (in millions) with their estimated useful lives (in years). The amounts are stated net of all prior asset impairment losses recognized.
|  |  | December 31,
| Estimated Useful Life | 2017 |  | 2016
Electric generation and distribution facilities | 8 - 40 |  | $ | 21,529 |  |  | $ | 22,337 |
Other buildings | 5 - 71 |  | 1,971 |  |  | 1,906 |
Furniture, fixtures and equipment | 2 - 32 |  | 284 |  |  | 303 |
Other | 5 - 44 |  | 335 |  |  | 365 |
Total electric generation and distribution assets and other |  |  | 24,119 |  |  | 24,911 |
Accumulated depreciation |  |  | (7,942 | ) |  | (7,919 | )
Net electric generation and distribution assets and other |  |  | $ | 16,177 |  |  | $ | 16,992 |
The following table summarizes depreciation expense (including the amortization of assets recorded under capital leases and the amortization of asset retirement obligations) and interest capitalized during development and construction on qualifying assets for the periods indicated (in millions):
Years Ended December 31, |  | 2017 |  | 2016 |  | 2015
Depreciation expense |  | $ | 1,005 |  |  | $ | 1,002 |  |  | $ | 958 |
Interest capitalized during development and construction |  | 139 |  |  | 118 |  |  | 84 |
Property, plant and equipment, net of accumulated depreciation, of $10 billion was mortgaged, pledged or subject to liens as of December 31, 2017 and 2016, including assets classified as held-for-sale. The following table summarizes regulated and non-regulated generation and distribution property, plant and equipment and accumulated depreciation as of the dates indicated (in millions):
December 31, |  | 2017 |  | 2016
Regulated generation, distribution assets and other, gross |  | $ | 8,093 |  |  | $ | 7,815 |
Regulated accumulated depreciation |  | (3,357 | ) |  | (3,299 | )
Regulated generation, distribution assets and other, net |  | 4,736 |  |  | 4,516 |
Non-regulated generation, distribution assets and other, gross |  | 16,026 |  |  | 17,096 |
Non-regulated accumulated depreciation |  | (4,585 | ) |  | (4,620 | )
Non-regulated generation, distribution assets and other, net |  | 11,441 |  |  | 12,476 |
Net electric generation, distribution assets and other |  | $ | 16,177 |  |  | $ | 16,992 |
The following table presents amounts recognized related to asset retirement obligations for the periods indicated (in millions):
|  | 2017 |  | 2016
Balance at January 1 |  | $ | 357 |  |  | $ | 247 |
Additional liabilities incurred |  | 1 |  |  | 12 |
Liabilities settled |  | (21 | ) |  | (4 | )
Accretion expense |  | 16 |  |  | 15 |
Change in estimated cash flows |  | 25 |  |  | 86 |
Other |  | (10 | ) |  | 1 |
Balance at December 31 |  | $ | 368 |  |  | $ | 357 |
The Company's asset retirement obligations primarily include active ash landfills, water treatment basins and the removal or dismantlement of certain plants and equipment. The $25 million increase in estimated cash flows for 2017 is primarily related to the legal obligations for the demolition of the Huntington Beach Units in connection with the Southland re-powering project.

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- References No definition available. + Details
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- Definition The entire disclosure for long-lived, physical assets used in the normal conduct of business and not intended for resale. Includes, but is not limited to, accounting policies and methodology, roll forwards, depreciation, depletion and amortization expense, including composite depreciation, accumulated depreciation, depletion and amortization expense, useful lives and method used, income statement disclosures, assets held for sale and public utility disclosures. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -URI http://asc.fasb.org/topic&trid=2155823 + Details
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