Note 9. Intangible Assets, Net

Intangible assets are tested for impairment when changes in circumstances indicate the carrying value of those assets may not be recoverable. As of December 31, 2017 and 2016, there were no indications of impairment.

As disclosed in Note 3, we added $6.9 million of intangible assets in 2017 related to customer relationships acquired in the Vandalia acquisition with an estimated useful life of 15 years. The following table presents the carrying amount of intangible assets by segment and by major asset class.


	Autocam Precision Components Group			Precision Engineered Products Group			Total
Balance as of December 31, 2015	$	46,417		$	233,800		$	280,217
Amortization		(3,533	)		(22,465	)		(25,998	)
Currency impacts		44			—			44

Balance as of December 31, 2016	$	42,928		$	211,335		$	254,263
Additions		—			6,900			6,900
Amortization		(3,481	)		(19,979	)		(23,460	)
Currency impacts		(1	)		—			(1	)

Balance as of December 31, 2017	$	39,446		$	198,256		$	237,702


			December 31, 2017							December 31, 2016
	Estimated Useful Life in Years		Gross Carrying Value		Accumulated Amortization			Net Carrying Value		Gross Carrying Value		Accumulated Amortization			Net Carrying Value
Customer relationships		12 - 15	$	282,030	$	(52,408	)	$	229,622	$	275,130	$	(30,137	)	$	244,993
Other		1 - 15		19,200		(11,120	)		8,080		19,217		(9,947	)		9,270

Total identified intangible assets			$	301,230	$	(63,528	)	$	237,702	$	294,347	$	(40,084	)	$	254,263

The following table summarizes estimated amortization expense for the next five years:


Year Ending December 31,
2018	$	23,878
2019		23,810
2020		23,670
2021		23,678
2022		23,678