Property, Plant and Equipment
 9 Months Ended
Feb. 28, 2014
Property, Plant and Equipment [Abstract]  
Property, Plant and Equipment
Property, Plant and Equipment.
Property, plant and equipment are carried at cost less accumulated depreciation. Depreciation is computed using the straight-line method over the estimated useful life of the asset. Depreciation of instruments is included within selling, general and administrative expense. Related maintenance and repairs are expensed as incurred.
The Company reviews property, plant and equipment for impairment whenever events or changes in circumstances indicate that the carrying value of an asset may not be recoverable. An impairment loss would be recognized when estimated undiscounted future cash flows relating to the asset, or asset group, are less than its carrying value, with the amount of the loss equal to the excess of carrying value of the asset, or asset group, over the estimated fair value.
Useful lives by major product category consisted of the following:
 
 
Useful life
Land improvements
20 years
Buildings and leasehold improvements
30 years
Machinery and equipment
5-10 years
Instruments
4 years

 
Property, plant and equipment consisted of the following:
 
(in millions)
February 28, 2014
 
May 31, 2013
Land and land improvements
$
40.7

 
$
40.5

Buildings and leasehold improvements
115.5

 
106.3

Machinery and equipment
400.1

 
375.4

Instruments
801.3

 
710.5

Construction in progress
61.3

 
48.8

Total property, plant and equipment
1,418.9

 
1,281.5

Accumulated depreciation
(728.0
)
 
(616.3
)
Total property, plant and equipment, net
$
690.9

 
$
665.2



The Company recorded depreciation expense of $49.7 million and $48.6 million for the three months ended February 28, 2014 and 2013, respectively, and $141.5 million and $134.6 million for the nine months ended February 28, 2014 and 2013, respectively.