Intangible Assets

12 Months Ended

Dec. 31, 2016

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible Assets

Intangible Assets

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

	Gross		Accumulated Amortization			Net
December 31, 2016
Purchased technology	$	114,754	$	(102,967	)	$	11,787
Patents	6,472		(6,472		)	—
Customer lists	37,000		(34,784		)	2,216
Trade names	11,536		(7,964		)	3,572
Total intangible assets	$	169,762	$	(152,187	)	$	17,575
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

Intangible assets amortization expense was $12.7 million, $12.9 million and $13.3 million for the years ended December 31, 2016, 2015 and 2014. The Company’s purchased intangible assets have remaining useful lives of one to five years as of December 31, 2016. 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, 2016 is as follows (in thousands):

For the Years Ending December 31,	Estimated Intangible Amortization Amount
2017	$	10,713
2018	4,870
2019	790
2020	790
2021	412
Thereafter	—
Total estimated future amortization expense	$	17,575