except for long-term debt , the carrying amounts of the company 2019s other financial instruments are measured at fair value or approximate fair value due to the short-term nature of these instruments . asset retirement obligations 2014the company records all known asset retirement obligations within other current liabilities for which the liability 2019s fair value can be reasonably estimated , including certain asbestos removal , asset decommissioning and contractual lease restoration obligations . the changes in the asset retirement obligation carrying amounts during 2011 , 2010 and 2009 were as follows : ( $ in millions ) retirement obligations .

Table:
( $ in millions ) | asset retirement obligations
balance at january 1 2009 | $ 3
accretion expense | 0
payment of asset retirement obligation | 0
balance at december 31 2009 | 3
obligation relating to the future retirement of a facility | 17
accretion expense | 0
payment of asset retirement obligation | 0
balance at december 31 2010 | 20
obligation relating to the future retirement of a facility | 5
accretion expense | 0
payment of asset retirement obligation | 0
balance at december 31 2011 | $ 25
the company also has known conditional asset retirement obligations related to assets currently in use , such as certain asbestos remediation and asset decommissioning activities to be performed in the future , that were not reasonably estimable as of december 31 , 2011 and 2010 , due to insufficient information about the timing and method of settlement of the obligation .
accordingly , the fair value of these obligations has not been recorded in the consolidated financial statements .
environmental remediation and/or asset decommissioning of the relevant facilities may be required when the company ceases to utilize these facilities .
in addition , there may be conditional environmental asset retirement obligations that the company has not yet discovered .
income taxes 2014income tax expense and other income tax related information contained in the financial statements for periods before the spin-off are presented as if the company filed its own tax returns on a stand-alone basis , while similar information for periods after the spin-off reflect the company 2019s positions to be filed in its own tax returns in the future .
income tax expense and other related information are based on the prevailing statutory rates for u.s .
federal income taxes and the composite state income tax rate for the company for each period presented .
state and local income and franchise tax provisions are allocable to contracts in process and , accordingly , are included in general and administrative expenses .
deferred income taxes are recorded when revenues and expenses are recognized in different periods for financial statement purposes than for tax return purposes .
deferred tax asset or liability account balances are calculated at the balance sheet date using current tax laws and rates in effect .
determinations of the expected realizability of deferred tax assets and the need for any valuation allowances against these deferred tax assets were evaluated based upon the stand-alone tax attributes of the company , and an $ 18 million valuation allowance was deemed necessary as of december 31 , 2011 .
no valuation allowance was deemed necessary as of december 31 , 2010 .
uncertain tax positions meeting the more-likely-than-not recognition threshold , based on the merits of the position , are recognized in the financial statements .
we recognize the amount of tax benefit that is greater than 50% ( 50 % ) likely to be realized upon ultimate settlement with the related tax authority .
if a tax position does not meet the minimum statutory threshold to avoid payment of penalties , we recognize an expense for the amount of the penalty in the period the tax position is claimed or expected to be claimed in our tax return .
penalties , if probable and reasonably estimable , are recognized as a component of income tax expense .
we also recognize accrued interest related to uncertain tax positions in income tax expense .
the timing and amount of accrued interest is determined by the applicable tax law associated with an underpayment of income taxes .
see note 12 : income taxes .
under existing gaap , changes in accruals associated with uncertainties are recorded in earnings in the period they are determined. .

Question: what was the net increase in aro during the period , in millions?
Answer: 22
Calculation: subtract(25, 3)