Intangibles

The components of intangible assets were:



(in thousands)	Weighted Average Amortization Period	Amortization Method	Cost		Accumulated Amortization		Net Carrying Amount
Customer relationships	6 years	Straight-line	$	274,000	$	3,806	$	270,194
Trademarks	3 years	Straight-line	10,000		278		9,722
Intangible assets, net					$	4,084	$	279,916

Amortization expense for the nine months ended January 31, 2018 was $4.1 million. Based on the carrying amounts of amortizable intangible assets noted above, estimated amortization expense for the next five 12-month periods beginning in January 31, 2018 is $49.0 million, $49.0 million, $48.7 million, $45.7 million and $45.7 million, respectively.