Goodwill and Other Intangible Assets (Notes)

6 Months Ended

Jun. 30, 2021

Goodwill and Intangible Assets Disclosure [Abstract]

The changes in the carrying value of goodwill by reportable segment for the six months ended June 30, 2021 are as follows:


(in millions)	Audio		Precision Devices		Total
Balance at December 31, 2020	$	878.8	$	31.2	$	910.0
Acquisition	—		31.4		31.4

Balance at June 30, 2021	$	878.8	$	62.6	$	941.4

The gross carrying value and accumulated amortization for each major class of intangible assets are as follows:


	June 30, 2021				December 31, 2020
(in millions)	Gross Carrying Amount		Accumulated Amortization		Gross Carrying Amount		Accumulated Amortization
Amortized intangible assets:
Trademarks	$	2.0	$	0.4	$	1.0	$	0.4
Patents	40.8		38.4		40.8		36.1
Customer relationships	39.7		6.7		12.0		5.2
Developed technology	41.7		9.8		36.5		6.7
Other	2.4		1.0		1.8		0.7
Total	126.6		56.3		92.1		49.1
Unamortized intangible assets:
Trademarks	32.0				32.0
IPR&D (1)	3.7				3.7
Total	35.7				35.7
Total intangible assets, net	$	106.0			$	78.7

(1) The in-process research and development ("IPR&D") project is expected to be complete in 2021. Upon completion of the underlying project, IPR&D will be reclassified as a definite-lived intangible asset and amortized over its estimated useful life.

Amortization expense totaled $3.9 million and $3.2 million for the three months ended June 30, 2021 and 2020, respectively. For the six months ended June 30, 2021 and 2020, amortization expense was $7.2 million and $6.5 million, respectively. Amortization expense for the next five years, based on current definite-lived intangible balances, is estimated to be as follows:


(in millions)
Q3-Q4 2021	$	8.6
2022	11.8
2023	11.2
2024	11.2
2025	10.8