text: on an annual basis or more often if events or circumstances warrant. A 
  cash generating unit is the smallest identifiable group of assets that 
  generates cash inflows that are largely independent of the cash inflows 
  from other assets or groups of assets. Goodwill and indefinite life 
  intangible assets are allocated to cash generating units (or groups of 
  cash generating units) based on the level at which management 
  monitors goodwill, which is not higher than an operating segment. The 
  allocation involves significant estimates of future cash flows, estimated 
  periods of use, applicable discount rates and considerable management 
  judgment, and is made to cash generating units (or groups of cash 
  generating units) that are expected to benefit from the synergies of the 
  business combination. If key estimates differ unfavourably in the future, 
  we could experience impairment charges that could decrease net 
  income. We did not record an impairment charge in 2013 since the 
  the cash generating units exceeded their 
  recoverable amounts of 
  carrying values. In 2012, we recorded an impairment charge of $80 
  million related to certain Media assets, due to the challenging economic 
  conditions, weakening industry expectations and a decline in 
  advertising revenues. 
  
  The table below shows what the impact of an increase or decrease in 
  the primary assumptions and estimates on our accrued benefit 
  obligation and pension expense for 2013 would be: 