For acquired businesses, we record assets acquired and liabilities assumed at their estimated fair values on the respective acquisition dates. Based on these values, the excess purchase prices over the fair value of the net assets acquired is recorded as goodwill. Of the $710.1 million total goodwill at March 31, 2020, $474.8 million related to the North America Storage Solutions segment, $54.0 million related to the U.K. Storage Solutions segment and $181.2 million related to the Tank & Pump Solutions segment.

The following table shows the activity and balances related to goodwill from January 1, 2020 to March 31, 2020 (in thousands):

Intangible assets are amortized over the estimated useful life of the asset utilizing a method which reflects the estimated pattern in which the economic benefits will be consumed. Customer relationships are amortized based on the estimated attrition rates of the underlying customer base. Other intangibles are amortized using the straight-line method. When the intangible reaches the end of its life and no longer has value to the Company, the gross carrying amount and the related accumulated amortization is removed from our balance sheet.

The following table reflects balances related to intangible assets for the periods presented:

		March 31, 2020							December 31, 2019
	Estimated Useful Life in Years	Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount		Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount
		(In thousands)
Customer relationships	15 - 20	$	95,287	$	(45,833	)	$	49,454	$	94,808	$	(44,846	)	$	49,962
Trade names/trademarks	5 - 7		5,200		(4,246	)		954		5,200		(4,164	)		1,036
Non-compete agreements	5		300		(103	)		197		1,810		(1,648	)		162
Other	20		59		(35	)		24		60		(35	)		25
Total		$	100,846	$	(50,217	)	$	50,629	$	101,878	$	(50,693	)	$	51,185

Amortization expense for amortizable intangibles was approximately $1.5 million and $1.6 million for the three-month periods ended March 31, 2020 and 2019, respectively. Based on the carrying value at March 31, 2020, future amortization of intangible assets is expected to be as follows for the years ended December 31 (in thousands):