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Component: (Network and Table)
Network
2307301 - Disclosure - Asset Retirement Obligations (Tables)
(http://www.northwesternenergy.com/role/AssetRetirementObligationsTables)
Table(Implied)
Slicers (applies to each fact value in each table cell)
Reporting Entity [Axis]0000073088 (http://www.sec.gov/CIK)
Asset Retirement Obligation Disclosure [Abstract]Period [Axis]
2016-01-01 - 2016-12-31
Asset Retirement Obligation Disclosure [Abstract]
 
Schedule of Change in Asset Retirement Obligation
The following table presents the change in our gross conditional ARO (in thousands):

 
December 31,
 
2016
 
2015
Liability at January 1,
$
35,532

 
$
21,435

Accretion expense
1,885

 
1,437

Liabilities incurred
164

 
12,682

Liabilities settled
—

 
(22
)
Revisions to cash flows
1,821

 
—

Liability at December 31,
$
39,402

 
$
35,532