Goodwill and Other Intangible Assets
 3 Months Ended
Mar. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]  
Goodwill and Other Intangible Assets
Goodwill and Other Intangible Assets

Goodwill is reviewed for impairment annually or more frequently if impairment indicators arise. The Company allocates goodwill to both the PBM and HCIT segments. There were no impairments of goodwill during the three months ended March 31, 2015 and 2014.
The changes in the carrying amounts of goodwill by reportable segment for the three months ended March 31, 2015 are as follows (in thousands):
 
PBM
 
HCIT
 
Total
Balance at December 31, 2014
$
4,704,974

 
$
19,665

 
$
4,724,639

Acquisition (a)
199,026

 
—

 
199,026

Balance at March 31, 2015
$
4,904,000

 
$
19,665

 
$
4,923,665



(a)
Initial goodwill recorded in connection with the acquisition of Salveo in January 2015.

Definite-lived intangible assets are amortized over the useful lives of the related assets. The components of intangible assets were as follows (in thousands):
 
March 31, 2015
 
December 31, 2014
 
Gross Carrying Amount
 
 Accumulated Amortization
 
Net
 
Gross Carrying Amount
 
 Accumulated Amortization
 
Net
Customer relationships
$
1,552,022

 
$
603,064

 
$
948,958

 
$
1,527,722

 
$
564,623

 
$
963,099

Non-compete agreements
11,920

 
7,044

 
4,876

 
11,920

 
7,435

 
4,485

Other intangible assets
28,100

 
1,454

 
26,646

 
3,060

 
2,445

 
615

Total
$
1,592,042

 
$
611,562

 
$
980,480

 
$
1,542,702

 
$
574,503

 
$
968,199



Total amortization associated with intangible assets at March 31, 2015 is estimated to be $151.5 million for the remainder of 2015, $176.8 million in 2016, $157.8 million in 2017, $147.7 million in 2018, $137.6 million in 2019, $119.4 million in 2020 and $89.7 million in total for years after 2020.