XML 198 R20.htm IDEA: XBRL DOCUMENT v2.4.0.8
Asset Retirement Obligations (AROs)
 6 Months Ended
Jun. 30, 2013
Asset Retirement Obligations [Line Items]  
Asset Retirement Obligations (AROs)
ASSET RETIREMENT OBLIGATIONS (AROs)
A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):
 
Alliant Energy
 
IPL
 
WPL
 
2013
 
2012
 
2013
 
2012
 
2013
 
2012
Balance, January 1

$101.5

 

$91.1

 

$45.5

 

$56.2

 

$46.9

 

$34.9

Revisions in estimated cash flows (a)
3.4

 
(9.9
)
 
0.8

 
(9.2
)
 
2.6

 
(0.7
)
Liabilities settled
(0.1
)
 
(1.8
)
 
—

 
(1.7
)
 
(0.1
)
 
(0.1
)
Liabilities incurred
—

 
0.7

 
—

 
—

 
—

 
—

Accretion expense
1.8

 
1.8

 
0.8

 
1.0

 
0.8

 
0.8

Balance, June 30

$106.6

 

$81.9

 

$47.1

 

$46.3

 

$50.2

 

$34.9


(a)
For the six months ended June 30, 2012, IPL recorded revisions in estimated cash flows of ($8.2) million based on revised remediation timing and cost information for asbestos remediation at its Sixth Street Generating Station.
IPL [Member]
  
Asset Retirement Obligations [Line Items]  
Asset Retirement Obligations (AROs)
ASSET RETIREMENT OBLIGATIONS (AROs)
A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):
 
Alliant Energy
 
IPL
 
WPL
 
2013
 
2012
 
2013
 
2012
 
2013
 
2012
Balance, January 1

$101.5

 

$91.1

 

$45.5

 

$56.2

 

$46.9

 

$34.9

Revisions in estimated cash flows (a)
3.4

 
(9.9
)
 
0.8

 
(9.2
)
 
2.6

 
(0.7
)
Liabilities settled
(0.1
)
 
(1.8
)
 
—

 
(1.7
)
 
(0.1
)
 
(0.1
)
Liabilities incurred
—

 
0.7

 
—

 
—

 
—

 
—

Accretion expense
1.8

 
1.8

 
0.8

 
1.0

 
0.8

 
0.8

Balance, June 30

$106.6

 

$81.9

 

$47.1

 

$46.3

 

$50.2

 

$34.9


(a)
For the six months ended June 30, 2012, IPL recorded revisions in estimated cash flows of ($8.2) million based on revised remediation timing and cost information for asbestos remediation at its Sixth Street Generating Station.
WPL [Member]
  
Asset Retirement Obligations [Line Items]  
Asset Retirement Obligations (AROs)
ASSET RETIREMENT OBLIGATIONS (AROs)
A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):
 
Alliant Energy
 
IPL
 
WPL
 
2013
 
2012
 
2013
 
2012
 
2013
 
2012
Balance, January 1

$101.5

 

$91.1

 

$45.5

 

$56.2

 

$46.9

 

$34.9

Revisions in estimated cash flows (a)
3.4

 
(9.9
)
 
0.8

 
(9.2
)
 
2.6

 
(0.7
)
Liabilities settled
(0.1
)
 
(1.8
)
 
—

 
(1.7
)
 
(0.1
)
 
(0.1
)
Liabilities incurred
—

 
0.7

 
—

 
—

 
—

 
—

Accretion expense
1.8

 
1.8

 
0.8

 
1.0

 
0.8

 
0.8

Balance, June 30

$106.6

 

$81.9

 

$47.1

 

$46.3

 

$50.2

 

$34.9


(a)
For the six months ended June 30, 2012, IPL recorded revisions in estimated cash flows of ($8.2) million based on revised remediation timing and cost information for asbestos remediation at its Sixth Street Generating Station.