Goodwill and Other Intangible Assets

Goodwill represents the excess cost over fair value of identifiable net assets of businesses acquired. Changes in goodwill were as follows (in millions):



	United States		International			Total
Balance at December 31, 2017	$	486.5	$	47.1		$	533.6
Currency translation adjustments	—		(3.4		)	(3.4		)
Balance at December 30, 2018	$	486.5	$	43.7		$	530.2
Increase for acquisition activity (Note 4)	9.5		—			9.5
Currency translation adjustments	—		1.6			1.6
Balance at December 29, 2019	$	496.0	$	45.3		$	541.3

Components of intangible assets, net were as follows (in millions):



		December 29, 2019							December 30, 2018
	Useful Lives (in years)	Gross Carrying Amount		Accumulated Amortization			Carrying Value		Gross Carrying Amount		Accumulated Amortization			Carrying Value
Customer relationships	12 - 17	$	370.9	$	(313.5	)	$	57.4	$	361.5	$	(286.7	)	$	74.8
Tradenames	15 - Indefinite	58.6		(1.7		)	56.9		57.8		(1.7		)	56.1
Computer software & technology	3 - 7	188.1		(150.7		)	37.4		161.9		(132.0		)	29.9
Covenants not to compete	1 - 5	—		—			—		14.6		(14.5		)	0.1
Total		$	617.6	$	(465.9	)	$	151.7	$	595.8	$	(434.9	)	$	160.9

The carrying amount of tradenames with an indefinite life was $56.0 million at December 29, 2019 and 2018.

Amortization expense for intangibles assets was $44.3 million, $43.6 million and $43.9 million for the years ended December 29, 2019, 2018 and 2017, respectively. Estimated amortization expense of the existing intangible assets is as follows:



	Amount
Fiscal year ending 2020	$	33.1
Fiscal year ending 2021	23.7
Fiscal year ending 2022	17.3
Fiscal year ending 2023	10.8
Fiscal year ending 2024	4.5
Thereafter	6.3
	$	95.7