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Asset Retirement Obligations
 12 Months Ended
Dec. 31, 2016
Asset Retirement Obligation Disclosure [Abstract]  
ASSET RETIREMENT OBLIGATIONS
ASSET RETIREMENT OBLIGATIONS

We have recorded AROs primarily for asbestos abatement at certain generation and substation facilities, the removal and dismantlement of generation facilities, and the closure of fly-ash landfills at our generation facilities. We establish regulatory assets and liabilities to record the differences between ongoing expense recognition under the ARO accounting rules and the ratemaking practices for retirement costs authorized by the applicable regulators. On our balance sheets, AROs are recorded within other long-term liabilities.

The following table shows changes to our AROs during the years ended December 31:
(in millions)
 
2016
 
2015
 
2014
Balance as of January 1
 
$
58.7

 
$
40.5

 
$
39.4

Accretion
 
3.0

 
2.3

 
2.2

Additions
 
—

 
15.9

*
—

Liabilities settled
 
(0.2
)
 
—

 
(1.1
)
Balance as of December 31
 
$
61.5

 
$
58.7

 
$
40.5


*
During 2015, an ARO was recorded for the fly-ash landfills located at our generation facilities.