Goodwill
 3 Months Ended
Mar. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]  
Goodwill Goodwill
 
Goodwill arises because the purchase price paid for our acquisitions reflects numerous factors, including the strategic fit and expected synergies these acquisitions bring to our existing operations. Goodwill is recorded at fair value and is reviewed at least annually for impairment.
The following table provides the components of and changes in the carrying amount of goodwill (in millions):
 
 
Aviation
 
Land
 
Total
Balance as of December 31, 2017
 
$
326.9

 
$
518.5

 
$
845.5

Additions
 
—

 
13.7

 
13.7

Foreign exchange and other adjustments
 
(1.4
)
 
9.1

 
7.7

Balance as of March 31, 2018
 
$
325.5

 
$
541.3

 
$
866.9