Intangible Assets

12 Months Ended

Dec. 31, 2015

Intangible Assets [Abstract]

Intangible Assets

Intangible Assets

The following tables summarize the Company’s total purchased intangible assets (in thousands):

	Gross		Accumulated Amortization			Net
December 31, 2015
Purchased technology	$	114,754	$	(95,260	)	$	19,494
Patents	6,472		(6,472		)	—
Customer lists	37,000		(30,534		)	6,466
Trade names	11,536		(7,174		)	4,362
Backlog	2,127		(2,127		)	—
Total intangible assets	$	171,889	$	(141,567	)	$	30,322
December 31, 2014
Purchased technology	$	114,754	$	(87,398	)	$	27,356
Patents	6,472		(6,472		)	—
Customer lists	37,000		(26,284		)	10,716
Trade names	11,536		(6,384		)	5,152
Backlog	2,127		(2,127		)	—
Total intangible assets	$	171,889	$	(128,665	)	$	43,224

Intangible assets amortization expense was $12.9 million, $13.3 million and $13.8 million for the years ended December 31, 2015, 2014 and 2013. The Company’s purchased intangible assets have remaining useful lives of two to six years as of December 31, 2015. The Company reviews for impairment all of its purchased intangible assets whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable.

The estimated future amortization expense of purchased intangible assets as of December 31, 2015 is as follows (in thousands):

For the Years Ending December 31,	Estimated Intangible Amortization Amount
2016	$	12,747
2017	10,713
2018	4,870
2019	790
2020	790
Thereafter	412
Total estimated future amortization expense	$	30,322